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Biomedical subjects

T Y Chan

Publications and source records attributed to T Y Chan.

At least 109 records · Page 6Linked to original sources
PubMed1996

Food-borne nitrates and nitrites as a cause of methemoglobinemia.

Methemoglobinemia is a potentially fatal condition. Previous reports of toxic methemoglobinemia due to food-borne nitrates and nitrites are reviewed. Contamination of food during manufacture or degradation of nitrates in vegetables appear to be the most important factors. Some food items, such as refrigerated "dim-sum", stuffed pork and Chinese sausages, are very popular among some Asian populations; a stringent control against the excessive use of nitrates and nitrites is required in order to prevent outbreaks of toxic methemoglobinemia. Patients with glucose-6-phosphate dehydrogenase deficiency, a common condition in some Asian populations, may present with methemoglobinemia and intravascular hemolysis following exposure to oxidant drugs or chemicals. Methylene blue is inefficient and may exacerbate hemolysis in these patients; partial exchange transfusion may be required.

Adolescent↗
PubMed1995

Mechanisms mediating NG-nitro-L-arginine methyl ester-induced hypophagia in mice.

NG-Nitro-L-arginine methyl ester (50 mg/kg s.c.), an inhibitor of nitric oxide (NO) synthase, has been reported to increase brain serotonin (5-hhydroxytryptamine, 5-HT) metabolism and induce hypophagia. Conversely, enhanced NO synthase activity is found to be accompanied by a decrease in 5-HT level. This negative correlation between NO and 5-HT in the regulation of food intake was further studied in mice. 5-HT depletion by p-chlorophenylalanine (250 mg/kg i.p., twice daily for 2 days) failed to antagonize the hypophagic effect of NG-nitro-L-arginine methyl ester. Similarly, treatment with the NO synthesis precursor, L-arginine (1000 mg/kg s.c.), did not reverse the anorexia induced by fenfluramine (10 mg/kg s.c.), a 5-HT releaser/uptake inhibitor. Pretreatment with (-)-pindolol, methylsergide and ritanserin had no effect on the hypophagic action of NG-nitro-L-arginine methyl ester, suggesting the lack of involvement of 5-HT1 and 5-HT2 receptors. The selective neuronal NO synthase inhibitor, 7-nitroindazole (12.5-50.0 mg/kg i.p.), however, did not exhibit any hypophagic effect whilst NG-nitro-L-arginine methyl ester increased gastric retention, which may subsequently induce satiety. Moreover, the hypophagic effect of NG-nitro-L-arginine methyl ester, which was unassociated with changes in water intake and malaise induction, was also unattenuated by cholecystokinin (CCK) receptor antagonists, devazepide (10 mg/kg i.p.) and PD 135,158 ([1S-[1 alpha,2 beta[S*(S*)],4 alpha ]]-4-[[2-[[3-(1 H-indol-3-yl)-2-methyl-1-oxo-2-[[[(1,7,7- trimethylbicyclo[2.2.1]hept-2-yl)oxy]carbonyl]amino]propyl]amino] -1-phenylethyl] amino]-4-oxo-butanoic acid N-methyl-D-glucamine salt; 1 mg/kg i.p.).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Energy metabolism in hypoxic astrocytes: protective mechanism of fructose-1,6-bisphosphate.

The protective effects of fructose-1,6-biphosphate (FBP) during hypoxia/ischemia are thought to result from uptake and utilization of FBP as a substrate for glycolysis or from stimulation of glucose metabolism. To test these hypotheses, we measured CO2 and lactate production from [6-14C]glucose, [1-14C]glucose, and [U-14C]FBP in normoxic and hypoxic cultured astrocytes with and without FBP present. FBP had little effect on CO2 production by glycolysis, but increased CO2 production by the pentose phosphate pathway. Labeled FBP produced very small amounts of CO2. Lactate production from [1-, and 6-14C]glucose increased similarly during hypoxic hypoxia; the increase was independent of added FBP. Labeled lactate from [U-14C]FBP was minimal. We conclude that exogenous FBP is not used by astrocytes as a substrate for glycolysis and that FBP alters glucose metabolism.

Animals↗
PubMed1995

Effect of melatonin on the maintenance of cholesterol homeostasis in the rat.

The effect of melatonin on cholesterol metabolism in the rat was investigated in the dietary and hypothyroid models of hypercholesterolemia. In normal and dietary hypercholesterolemia (induced by 1% cholesterol, 0.5% bile acid), melatonin treatment (12.5mg/kg i.p.) reduced total serum cholesterol concentration and total low density lipoprotein (VLDL+LDL) cholesterol. The protective action of melatonin was manifested only following the induction of cholesterolemia in such animals. Enhanced catabolism of cholesterol to bile acids is likely involved as shown by an increase in fecal bile acid excretion following melatonin treatment. Incorporation of 1-14C acetate into sterols was unaffected by melatonin treatment which suggests its lack of influence on sterol biosynthesis. In secondary hypercholesterolemia (hypothyroidism induced by 2-thiouracil), melatonin exerted a beneficial effect by increasing the HDL/total LDL cholesterol ratio. These findings suggest that the hypocholesterolemic effect of melatonin may work through the augmentation of endogenous cholesterol clearance mechanisms. This is accompanied by the lowering of the cholesterol fraction associated with low density lipoproteins.

Animals↗
PubMed1995

Poisoning due to an over-the-counter hypnotic, Sleep-Qik (hyoscine, cyproheptadine, valerian).

The clinical features and risk of hepatotoxicity of 'Sleep-Qik' (valerian dry extract 75 mg, hyoscine hydrobromide 0.25 mg, cyproheptadine hydrochloride 2 mg) were determined in 23 patients treated in our hospital between 1988 and 1991. The main clinical problems were central nervous system depression and anticholinergic poisoning. There was no clinical evidence of acute hepatitis in the 23 patients after taking an average of 2.5 g of valerian (range 0.5 to 12 g). There was no evidence of subclinical liver damage in 12 patients who had routine liver function tests performed approximately 6-12 hours after ingestion. Delayed onset of severe liver damage was excluded in 10 patients in whom a telephone follow-up was possible. However, subclinical liver dysfunction in the acute stage (onset after 12-24 hours) and in the intervening period after discharge from hospital could not be excluded. To establish the risk of hepatotoxicity in long-term users and in those taking an overdosage of valerian, a much larger study of longer duration with serial liver function tests is clearly needed.

Adolescent↗
PubMed1995

Unrestricted availability of a plasma paracetamol assay service resulting in an increased number of inappropriate requests.

Previously, prior approval from the on-call chemical pathologist was required in our hospital for plasma paracetamol measurements. However, since May 1992, there have been no restrictions on ordering this assay. We have assessed the consequences of this policy change by comparing the number and appropriateness of requests for plasma paracetamol measurements in Chinese patients admitted to our hospital with acute poisoning over two six-month periods (July-December) in 1991 and 1993. Requests were considered appropriate if paracetamol ingestion was suspected or unknown drugs were ingested. The number of patients having plasma paracetamol concentrations assayed increased from 51 in 1991 to 141 in 1993 (176%). The corresponding increase in the number of Chinese patients admitted to two of our eight general wards with poisoning was estimated to be 93%. The proportion of 'appropriate' plasma paracetamol measurements dropped from 55% in 1991 to 21% in 1993. Eight patients had plasma paracetamol concentrations above the recommended treatment line; they were all from the group in whom the requests were appropriate. Three of the 135 patients in the group with 'inappropriate' requests were found to have slightly elevated but far from toxic plasma paracetamol concentrations. Unrestricted availability of plasma paracetamol measurements resulted in an increase in the number of inappropriate requests.

Acetaminophen↗
PubMed1995

Chemical gastro-oesophagitis, upper gastrointestinal haemorrhage and gastroscopic findings following Dettol poisoning.

1. Dettol liquid (chloroxylenol 4.8%, pine oil, isopropyl alcohol), a household disinfectant, has a corrosive action on the gastrointestinal mucosa when swallowed. The incidence of upper gastrointestinal haemorrhage and gastroscopic findings following Dettol poisoning was studied in 89 patients. 2. Five patients (5.6%) developed minor haematemesis, in the form of coffee-coloured or blood-stained vomitus. One patient had a gastroscopy performed on the day after admission, showing signs of chemical burns in the oesophagus and stomach. Gastroscopy was performed in one other patient on day 11 to rule out oesophageal stricture; the patient was normal. All patients completely recovered. 3. The data from this study suggest that upper gastrointestinal haemorrhage following Dettol poisoning tends to be mild and self-limiting. Gastroscopy, which may increase the risk of aspiration in patients with impaired consciousness, is not required unless other causes of gastrointestinal bleeding are suspected.

Adult↗
PubMed1995

The clinical value of screening for paracetamol in patients with acute poisoning.

In this retrospective study, we determined the clinical value of screening for paracetamol in 294 Chinese patients with acute poisoning presenting to the general medical wards at the Prince of Wales Hospital between January 1992 and June 1993. Of the 86 patients suspected of having ingested paracetamol, eight had levels above the recommended 'treatment line'. Of the 208 patients with no suspected paracetamol ingestion, four were found to have elevated but non-toxic plasma levels. The incidence of missed, potentially serious paracetamol poisoning in our patients with no suspected paracetamol ingestion is extremely uncommon. Routine screening of all patients with acute poisoning for toxic plasma paracetamol concentrations is therefore not indicated and should never be a substitute for thorough history taking and physical examination.

Acetaminophen↗
PubMed1995

The risk of aspiration in Dettol poisoning: a retrospective cohort study.

1. To determine if the risk of aspiration is increased in 'Dettol' (4.8% chloroxylenol, pine oil and isopropyl alcohol) poisoning and the factors that may be responsible, a study was made of 89 patients and 89 matched control subjects with other forms of poisoning admitted to the Prince of Wales Hospital, Hong Kong. 2. Aspiration was more common in patients with Dettol poisoning (8% vs 3%, P = 0.16). There were more control subjects with drowsiness at presentation (54% vs 24%, P < 0.0001), but the use of gastric lavage (88% vs 64%, P < 0.001) and the occurrence of vomiting (62% vs 17%, P < 0.0001) were more common in patients with Dettol poisoning. 3. Our findings suggest that Dettol poisoning may be associated with an increased risk of aspiration. This increase in risk may be related to the use of gastric lavage and the common occurrence of vomiting in patients with Dettol poisoning.

Adolescent↗
PubMed1995

Poisoning due to Chinese proprietary medicines.

1. To determine the toxic potentials of those Chinese proprietary medicines (CPM) which are commonly used for self-poisoning by adults in Hong Kong, all patients admitted to four of the eight general medical wards at the Prince of Wales Hospital between January 1988 and December 1993 were retrospectively studied. 2. There were 54 women and 17 men with their age ranging from 15 to 86 years. Twenty-three subjects (32%) also took alcohol, chemicals or drugs. Of the 51 subjects (72%) who had taken topical medicaments, 22 had no symptoms while 28 had minor features of gastrointestinal irritation (n = 26), mild (n = 2) or severe (n = 1) salicylate poisoning. Of the 17 subjects (24%) who had taken CPM tablets/capsules, nine had mild symptoms including nausea/vomiting and drowsiness. The three remaining patients (4%) who had ingested liquid CPM preparations were asymptomatic. Elevated plasma salicylate or paracetamol concentrations (> 0.1 mmol l-1) were found in some patients who had taken topical medicaments and CPM tablets/capsules, respectively. All the 71 patients completely recovered. 3. Most of the CPM used for self-poisoning in Hong Kong were of low to moderate toxicity except for those containing wintergreen oil (methyl salicylate).

Acetaminophen↗
PubMed1995

Neurotoxicity following the ingestion of a Chinese medicinal plant, Alocasia macrorrhiza.

1. A case of poisoning due to the raw root tuber of a Chinese medicinal plant, Alocasia macrorrhiza is presented. 2. The patient developed neurological (severe pain and numbness in the perioral area and throat) and gastrointestinal (nausea, vomiting, abdominal pain) symptoms immediately after eating the root tuber. 3. A macrorrhiza has properties and morphology very similar to another medical plant. A. odora. The root tuber of the latter is known to contain a neurotoxin sapotoxin.

Adult↗
PubMed1995

Low-dose dopamine in severe right heart failure and chronic obstructive pulmonary disease.

OBJECTIVE: To describe the beneficial effects of low-dose dopamine infusion (2-5 micrograms/kg/min) in a patient with severe cor pulmonale complicating chronic obstructive pulmonary disease (COPD). CASE SUMMARY: A 53-year-old woman with severe cor pulmonale and generalized edema complicating COPD received low-dose dopamine to stabilize blood pressure and, perhaps, improve cardiac output. Low-dose dopamine also improved her renal function and enhanced the diuretic response to furosemide therapy. DISCUSSION: Previous studies of dopamine in such patients were reviewed. Both dopamine infusion (4 micrograms/kg/min) and oral administration of its precursor, L-dopa, can increase the cardiac output, decrease pulmonary vascular resistance, and enhance oxygen delivery in patients who are stable with cor pulmonale secondary to COPD. In patients with COPD during acute respiratory failure, high-dose dopamine (10 micrograms/kg/min) has been shown to increase the diaphragmatic blood flow and contraction. Low-dose dopamine also has been reported to be useful in patients with congestive heart failure or cirrhosis of the liver. CONCLUSIONS: Low-dose dopamine is useful in the acute management of patients with severe cor pulmonale complicating COPD because of the drug's beneficial effects on blood pressure, cardiac output, renal perfusion, natriuresis, and diuresis. Low-dose dopamine also may enhance the natriuretic and diuretic response to loop diuretics, decrease pulmonary vascular resistance, and enhance oxygen delivery.

Cardiac Output, Low↗