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Biomedical subjects

Y S Chong

Publications and source records attributed to Y S Chong.

13 recordsLinked to original sources
PubMed2001

Molecules with shape memory based on restricted rotation.

[reaction--see text] Diimide 1 and octaimide 2 both adopt two stable conformations at room temperature as a result of restricted rotation about two C(aryl)-N(imide) single bonds, a compact "folded" and an open "unfolded" structure. Predictable ratios of folded and unfolded rotamers can be achieved by heating in solvents of appropriate polarity as measured by the Reichardt's parameter (E(T30)). On cooling to room temperature, the resulting conformational changes are "locked in" as restricted rotation is reestablished.

Journal Article↗
PubMed2001

Postpartum intrauterine pressure studies of the uterotonic effect of oral misoprostol and intramuscular syntometrine.

OBJECTIVES: To investigate the effect of oral misoprostol in dosages varying from 200 microg to 800 microg on postpartum uterine contractility and to establish their side effects. DESIGN: A prospective descriptive study. PARTICIPANTS: Fifty-seven women who delivered vaginally after spontaneous labours not requiring augmentation. METHODS: Within 5 minutes of delivery of the placenta, a calibrated Gaeltec catheter with an intrauterine pressure transducer at its tip was inserted transcervically into the uterine cavity. Cumulative uterine activity was recorded for 30 minutes in each woman before administering the oral misoprostol tablets and continued for a further 90 minutes after its administration. Thus each woman acted as her own control regarding changes in uterine contractility. Uterine activity was recorded on a Sonicaid Meridian fetal monitor, which measures active contraction area automatically. The incidence of side effects was also recorded. RESULTS: There was no statistical difference (P = 0.887) in the adjusted mean difference in cumulative uterine activity following all the doses of oral misoprostol, compared with intramuscular syntometrine, the largest difference being seen in oral misoprostol 200 microg (adjusted mean difference -2282 kPas s, 95% CI -7954 to 3390 kPas s). The mean onset of action of oral misoprostol (6.1, SD 2.1 min) was significantly slower than that of intramuscular syntometrine (3.2, SD 1.5 min; P = 0.002), but their durations of action were similar (P = 0.637). In the misoprostol group the commonest side effects were shivering (36%) and a rise in body temperature above 38 degrees C (40%). In the syntometrine group, the most commonly observed side effect was moderate uterine pain (nine out of ten women) and a rise in diastolic blood pressure of 20 mmHg (two out of ten women). CONCLUSION: The results of this study show that oral misoprostol has a definite uterotonic effect on the postpartum uterus. At doses of 200 microg to 400 microg, oral misoprostol has a similar uterotonic effect to intramuscular syntometrine. Higher doses of oral misoprostol are associated with significantly more side effects.

Administration, Oral↗
PubMed2000

Impaired vasoconstriction in pregnancy-induced hypertension assessed using doppler fluximetry.

OBJECTIVE: To determine whether there is a difference in peripheral vascular reactivity between normal women and those with pregnancy-induced hypertension. METHODS: Capillary blood flow (flux) was recorded in the skin over the ankle in 26 pregnant women with pregnancy-induced hypertension at term. Twelve of these women had proteinuria, and 14 were nonproteinuric. Leg lowering was used to activate the venoarteriolar reflex, and the resultant change in flux, expressed as a percentage change from the baseline, was used as an index of vascular reactivity. The results were compared with those of a control group comprising 23 matched normotensive women. The study was repeated on all of the women after delivery. RESULTS: Women with hypertension showed a median (range) increase in flux of +24.4% (-15.5% to +151.1%), significantly different from controls: -39.3% (-80.9% to -4.3%, P <.001). This difference persisted regardless of the presence or absence of proteinuria. Responses in women with pregnancy-induced hypertension were significantly different after delivery (median -60.7%; range -158.5% to -19.5%, P <.001) when compared with predelivery responses. Similar changes as a result of delivery were seen in women with proteinuric (medians +25.9% and -57. 9%, P <.002) and nonproteinuric (medians +7.8% and -62.8%, P <.001) hypertension but not in controls. Postdelivery responses in women with hypertension were no different from those of controls. CONCLUSION: Women with pregnancy-induced hypertension have abnormal cutaneous vascular reactivity that returns to normal after delivery.

Adult↗
PubMed1998

The reliability of catheter-tip transducers for the measurement of intrauterine pressure in the third stage of labour.

In order to assess the reliability of intrauterine pressure measurements in the third stage of labour, catheter-tip transducers were used in 20 women randomly allocated into two groups of 10. In each case in the first group two catheters were tied together and introduced transcervically into the uterine cavity after delivery of the placenta. In each case in the second group two catheters were inserted independently into the same uterine cavity. The active and cumulative active pressures recorded from the pairs of catheters within each uterine cavity were compared. Comparison of individual active pressure readings from separate transducers revealed good agreement whether the catheters were tied together or were separate. Cumulative active pressure was very similar when assessed by each catheter in the same uterus. Intrauterine catheter-tip transducers can be used reliably to measure uterine activity in the third stage of labour although there may be minor contraction by contraction differences in recordings of individual active pressures.

Catheterization↗
PubMed1998

Correlation of change in uterine activity to blood loss in the third stage of labour.

In 47 women, the change in the uterine activity after the administration of a uterotonic agent was correlated with the amount of blood loss during the same period of time. Uterine activity was measured by a Gaeltec catheter-tipped pressure transducer inserted transcervically within 5 min of delivery of the placenta. A uterotonic agent (either intravenous syntocinon, intramuscular syntometrine or oral misoprostol) was given after the insertion of the intrauterine pressure catheter and pressure recorded for another 90 min. Blood loss over the same 2-hour period was collected with absorbent paper which was then assessed by colorimetric measurement of the haemoglobin content in the sample. Our results show that the change in uterine activity is associated with the total blood loss. However, there is a poor linear correlation between the two variables probably because of the biological variation in myometrial activity and differences in coagulation mechanisms in normal women.

Blood Coagulation↗
PubMed1998

Cardiac arrest associated with sulprostone use during caesarean section.

Sulprostone, a synthetic prostaglandin with potent uterotonic action, has been shown to have a low complication rate in a large series. We present a case in which a bolus intravenous injection of sulprostone 30 micrograms was administered to treat postpartum haemorrhage during caesarean section. The 38-year-old patient with no previous cardiac or smoking history developed complete heart block, ventricular fibrillation and subsequent asystole. Cardiopulmonary resuscitation was successful after 45 minutes. Post resuscitation there was no myocardial infarction and she had complete neurological recovery. We postulate that the bolus of sulprostone resulted in possible coronary spasm that resulted in cardiac arrest.

Adult↗
PubMed1994

Myocardial protection during prolonged ischaemic cardiac arrest: experimental evaluation of three crystalloid cardioplegic solutions.

The aim of this study is to define the cardioprotective effects (functional and metabolic) of our modified "extracellular" cardioplegic solution (MBS: containing glucose, aspartate and lactobionate), St. Thomas' Hospital No. 2 (STH) and Bretschneider's No. 3 (Bret) solutions during prolonged hypothermic ischaemia (20 degrees C, 6 hours) in the isolated working rat heart. hearts (n = 9-10 in each group) were arrested with, and exposed to, multidose reinfusion (2 minutes every 40 minutes interval) throughout the ischaemic period with cold (4 degrees C) MBS, STH or oxygenated (95% O2: 5% CO2) Bret. All MBS treated hearts resumed spontaneous regular sinus rhythm (0.51 +/- 0.01 minutes) of contraction during post-ischaemic reperfusion for 30 minutes at 37 degrees C with the complete recovery of all the functional indices (aortic flow: 87.4 +/- 3.4%, cardiac output: 94.1% +/- 3.3%, coronary flow: 101.8 +/- 4.1%, heart rate: 99.8 +/- 2.8% and aortic pressure: 105.7 +/- 4.6% of prearrest control values). In contrast, hearts protected with either STH or Bret showed the poor or no post-ischaemic recovery of cardiac pump function (aortic flow: 7.2 +/- 4.8% and 0%, respectively). Recovery of all other left ventricular function indices were also significantly (p < 0.001) decreased with increasing more hearts failing to regain function (MBS: 0/10, STH: 7/9 and Bret: 9/9). The efflux of lactate during 6 hours ischaemic arrest was increased [52.40 +/- 1.50 v 36.8 +/- 1.70 (STH) or 14.45 +/- 0.70 (Bret) mumol/heart, p < 0.001] and the progressive increase in the coronary vascular resistance was completely abolished in MBS treated hearts. These improvements were associated with the reduction in the decline of the myocardial adenosine triphosphate (23.44 +/- 1.08 v 3.79 +/- 1.08 or 4.51 +/- 0.71 mumol/g dry wt), creatine phosphate (30.23 +/- 1.52 v 8.01 +/- 2.21 or 5.41 +/- 0.03 mumol/g dry wt) and guanosine triphosphate (2.26 +/- 0.23 v 0.24 +/- 0.11 or 0.59 +/- 0.07 mumol/g dry wt) during ischaemia, and total resynthesis after reperfusion (ATP: 92% v 36% or 25% and CP: 126% v 92% or 59% of control). These results indicate that the new cardioplegic solution, MBS can meet the metabolic demand of the ischaemic myocardium because of the greater synthesis of intramyocardial ATP and CP during cardioplegic arrest, provide substantially improved protection of hearts from injury and thus increase (double) the safe duration of cardiac arrest.

Animals↗
PubMed1993

Elderly patients with perforated peptic ulcers: factors affecting morbidity and mortality.

Morbidity and mortality of perforated peptic ulcers (PPUs) have been higher when they occur in elderly patients. Seventy-three PPUs were reviewed to determine the factors accounting for the poor outcome in patients at or above 65 years old (elderly PPU). The presentation of 44 young PPUs was compared to 29 elderly PPUs. Delay in diagnosis, associated comorbid factors and shock on admission were found to be the primary factors. There was a significant difference between the two groups in terms of duration of pain before the diagnosis was made (8.2 h vs 16.4 h) (P < 0.05). The delay in diagnosis was partly due to the vague presentation, as 41.4% (11 patients) of the elderly presented with abdominal pain not localized in the epigastrium. In addition, 55.2% (16) of elderly patients did not have a history of prior ulcer disease and one-third (nine) did not have air under the diaphragm on chest X-ray. Significant comorbid factors were present in 65.5% compared to 15.9% in the younger group (P < 0.001). Shock on admission was present in six (20.7%) elderly patients, but only in one (2.3%) young patient (P < 0.05). As a result, morbidity was 89.6% in the elderly group compared to 27.2% in the younger patients (P < 0.001). Wound complications accounted for a significant proportion of the morbidity. Mortality was 17.2% and 2.3% respectively (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1988

In vitro activities of eight antibiotics against methicillin-resistant S. aureus and S. epidermidis strains isolated in Korea.

Staphylococcus aureus and Staphylococcus epidermidis strains isolated at eight large medical centers in Korea were examined for methicillin resistance and resistance to eight other antibiotics; cefazolin, cefamandole, cefuroxime, cefoxitin, cefotaxime, moxalactam, penicillin G and vancomycin. Methicillin resistance was found in 296 of 1225 strains (24.2%) of S. aureus and 126 of 348 strains (36.2%) of S. epidermidis. Methicillinresistant strains were isolated from all sources with the frequency of isolation ranging from 11% to 60%. From pleural effusion, throat swab and blood, methicillin-resistant strains of S. aureus were more frequently isolated with statistical significance (Chi-squared test, 95% confidence). Almost all of Methicillin-resistant S. aureus (MRSA) and S. epidermidis (MRSE) strains were multiply resistant to one or more tested eight antibiotics. However only 7(2.4%) of 296 MRSA strains and 2(1.6%) of 126 MRSE strains were resistant to vancomycin. Vancomycin was the most effective antibiotic against staphylococcal isolates as well as MRSA and MRSE.

Anti-Bacterial Agents↗