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Biomedical subjects

F C Cheng

Publications and source records attributed to F C Cheng.

At least 73 records · Page 4Linked to original sources
PubMed1992

Simultaneous measurement of serotonin, catecholamines and their metabolites in cat and human plasma by in vitro microdialysis-microbore high-performance liquid chromatography with amperometric detection.

A method for the simultaneous measurement of norepinephrine, epinephrine, dopamine, 3,4-dihydroxyphenylacetic acid, homovanillic acid, serotonin and 5-hydroxyindole-3-acetic acid in cat and human plasma by in vitro microdialysis-microbore high-performance liquid chromatography with electrochemical detection is described. The detection limit (signal-to-noise ratio = 3) is about 0.05-0.1 pg per injection. The volume of plasma samples required is very small (< 200 microliters), hence there is minimal blood loss in repeated blood sampling, especially in experiments using small animals. Within 15 min, a fast isocratic separation of these analytes by using a microbore reversed-phase ODS column is achieved, hence over 90 analyses can be performed in a single working day. As microdialysis per se is not destructive to plasma samples, the remaining plasma sample and perfusate can be repeatedly analysed for other substances. This simple, efficient and sensitive method can therefore be used as a routine clinical and basic research technique in the investigation of blood biogenic amines and their metabolites.

Animals↗
PubMed1991

[Ultrastructural observation on the oocyst development and sporozoite formation of Plasmodium vivax].

The oocyst development of Plasmodium vivax was heralded by the appearance of cytoplasmic vacuoles and membraneous clefts. These clefts broke up oocyst cytoplasm into many sporoblasts. The onset of transformation from oocyst to sporozoite was heralded by forming pellicular complex, at some point of pelliculum of sporoblast dense inner membrane and subpellicular microtubules formed beneath the plasmalemma. The pellicular complex bulged out to form sporozoite buds appearing as small domes. Following enlargement of sporozoite buds the apical ends of the buds became conical in longitudinal sections with the newly formed apical rings at their truncated apices and then, newly formed dense inner membranes and subpellicular microtubules gradually extended backwards and finally enclosed the sporozoites. Beneath the inner membrane there were a total of 10-12 subpellicular microtubules arranged irregularly as 5 + 6, 6 + 5, 6 + 6, 7 + 4, 8 + 3, 10 + 1 and 11 + 1. During the formation of sporozoite, intranuclear spindle appeared in the nucleus, suggesting that the second meiosis in the life cycle of Plasmodium vivax occurred in developing sporozoites.

Animals↗
PubMed1990

Electrochemical oxidation of 5-hydroxytryptophol. I: Studies in acid solution.

The oxidation chemistry of the endogenous central nervous system indole 5-hydroxytryptophol (5-HTOL) has been studied at pH 2 using electrochemical methods. The first voltammetric oxidation peak (I) appears to involve an initial one-electron abstraction giving a transient radical cation that, in the rate-controlling step, deprotonates to give a neutral radical. A radical-substrate reaction then occurs to give a dimer radical which is further oxidized to yield three simple dimers (4,4'-,4,6'-, and 2,4'-linked). The neutral radical can be further oxidized (1e) to a quinone imine that, as a result of very fast follow-up chemistry and electrochemistry, yields tryptophol-4,5-dione (B) which has been isolated in pure form. Reactions between intermediate species also result in three dimers containing residues of 5-HTOL and B and an unusual oxygen-bridged trimer.

5-Hydroxytryptophan↗
PubMed1990

Degradation mechanism of nefopam in solution under stressed storage conditions.

Nefopam, in pH 2.0 and pH 9.0 solutions, was forcibly degraded at 90 +/- 0.2 degrees C for 60 days. At least eight degradation products from the above solutions were collected from a reverse-phase high performance liquid chromatographic (HPLC) system with a C18 semipreparative column. Some minor peaks were considered insignificant, and no attempt was made to collect and identify their structures. The collected eluents under each major peak were further purified by extraction with methylene chloride from alkaline solutions. Proton nuclear magnetic resonance and fast atom bombardment mass spectroscopy were used to characterize the chemical properties of these degradates. The chemical structures of the major degradation products were proposed as (B) or (C) 2,3-dihydro-2(2'-hydroxyethyl)-N-methyl-1-phenyl-isoindole; (D) or (E) 1-hydroxy-3,4,5,6-tetrahydro-5-methyl-1-phenyl-1H-2,5-benzoxazocine++ +; (F) 2-(N-(2-hydroxyethyl)-N-methylaminomethyl) benzhydrol; (G) 2-(N-(2-hydroxyethyl)-N-methylaminoethyl) benzophenone; (H) 1-hydroxy-3,4,5,6-tetrahydro-5-methyl-1-phenyl-1H-2,5-benzoxazocine++ +, where B and C, D and E, are diasteromers. The possible pathways by which the nefopam degradation proceeded in acidic and basic solutions is postulated as Schemes I and II, respectively. The initial ring-opening process at the site of ether linkage appears to be the rate-determining step of degradation in both acidic and basic solutions.

Chemical Phenomena↗
PubMed1982

Serotypes of Escherichia coli isolated from patients with recurrent pyogenic cholangitis.

Strains of Escherichia coli were isolated from laparotomy specimens from Chinese patients with recurrent pyogenic cholangitis in Hong Kong. A large variety of serotypes were found. Several sites were sampled in each patient. While only one serotype was normally isolated from one site, different sites often yielded different serotypes in the same patient. Generally the 'O' types found did not correspond to those found in the faeces of the Hong Kong Chinese population.

Bile↗
PubMed1981

Carcinoma of the gallbladder.

A retrospective study of 100 proved cases of primary carcinoma of the gallbladder admitted to the University Surgical Unit, University of Hong Kong, over a 20-year period was undertaken. The female to male ratio was 1.4 to 1. The peak incidence was in the seventh decade for the females and the sixth decade for the males. Preoperative diagnosis was made in 10 patients. "Curative" cholecystectomy was performed in 20 patients with a 5-year survival rate of 10 per cent. Palliative procedures were performed in 44 patients with a median survival of 8 weeks, which was not significantly different from that in the 30 patients who were not operated upon or had laparotomy and biopsy only. Radical resection was carried out in 6 patients, all of whom died in hospital. Gallstones were found in only 26 patients. The gallbladders of 3 patients had associated benign tumours, one of which had malignant transformation at multiple sites. One patient had chronic typhoid infection. The incidence of clonorchis infestation and primary pyogenic cholangitis in these 100 patients was not different from that of our general hospital population.

Adult↗
PubMed1981

The bacteriology of recurrent pyogenic cholangitis and associated diseases.

Ninety-five patients with recurrent pyogenic cholangitis had a range of specimens taken at laparotomy for bacterial culture. Bacteria were isolated from 68% of cases. Escherichia coli was the predominant pathogen. Other aerobic and anaerobic intestinal bacteria were also isolated. Liver biopsy, bile and gallstones were the most rewarding specimens for culture. Infection was usually localized, but systemic infection occurred occasionally. The site of infection is probably in the liver parenchyma; however, the route by which intestinal bacteria invade the liver is not known. Sixty per cent of the cases of recurrent pyogenic cholangitis had gallstones and 20% were infected with Clonorchis sinensis.

Bile↗
PubMed1981

The treatment of second degree haemorrhoids by injection, rubber band ligation, maximal anal dilatation, and haemorrhoidectomy: a prospective clinical trial.

One hundred and twenty patients with confirmed second degree haemorrhoids were randomly allocated to four treatment groups; injection, rubber band ligation, maximal anal dilatation, and haemorrhoidectomy. Each groups consisted of 30 patients. All patients were regularly followed up for at least one year. Assessment at one year showed that haemorrhoidectomy "cured" the haemorrhoids in 29 out of 30 patients. Rubber band ligation relieved 25 out of 30 and maximal anal dilatation 24 out of 30. Injection was the least effective treatment, and relieved 18 of the 30 patients, with a cure rate of 60% only. Haemorrhoidectomy caused pain in all cases, anal stenosis in two, postoperative haemorrhage in two, and the patients required an average hospital stay of 11.5 days and an average of a further 15.5 days off work. Rubber band ligation was painless in 26 patients out of 30, and maximal anal dilatation was painless in 25 our of 30. There were no postoperative complications in the latter two treatment groups. Haemorrhoidectomy is good in "curing" the disease, but the higher possibility of postoperative pain and complications and longer hospital stay would not justify its use in the treatment of second degree haemorrhoids. Both rubber band ligation and maximal anal dilatation are effective and relatively free from complications. Rubber band ligation has the additional advantage of not requiring hospital stay or anaesthesia and is therefore considered to be the most appropriate method of treatment for second degree haemorrhoids.

Adult↗
PubMed1980

Operative cholangiography: evaluation of its routine use in 569 cholecystectomies.

From 1974 till 1979, 569 cholecystectomies with routine operative cholangiography were performed in the university surgical unit, Kwong Wah Hospital, Hong Kong, for non-malignant disease of the gallbladder. Gallstones were present in 522 cases. Acalculous cholecystitis occurred in 47 cases. At least one of the clinical or operative indications to explore the common bile duct was present in 312 of the patients. However, in this group of patients in whom routine operative cholangiography was done, exploration of the common bile duct was performed in only 147, thus avoiding unnecessary exploration of the duct in 165 cases (52.8%). In the remaining 257 patients in whom there was no indication to explore the common bile duct, operative cholangiography revealed unexpected stones in the common bile duct in 14 (5.5%). After choledochotomy, post exploratory operative T-tube cholangiography was performed to rule out overlooked stones, which were present in six cases (6/161, i.e., 3.7%). Postoperative T-tube cholangiography performed on the 12th to the 14th postoperative day showed retained stones in 17 cases, giving an incidence of known retained stones of 11% (17/161) of cholecystectomies with exploration of the common bile ducts, or 3% (17/569) in the whole series of cholecystectomies.

Adult↗
PubMed1978

The interrelationship between bleeding, perforation, and stenosis in duodenal ulceration.

The interrelationship of gastrointestinal bleeding, acute perforation, and pyloroduodenal stenosis was examined in a hospital series of 1,457 patients with duodenal ulcers. The proportion of each complication among the total number of ulcer patients after various periods of ulcer symptoms was determined. There was little variation in the proportion with bleeding as the duration of symptoms increased, whereas the proportion with perforation decreased and the proportion with stenosis increased with increasing duration of ulcer dyspepsia. The association of bleeding with perforation (26 patients) was more common than the association of bleeding with stenosis (12 patients), and more so than the association of perforation with stenosis (4 patients). To explain the paradoxical relationship of perforation and stenosis it was proposed that perforation occurred when the pathological process in ulceration was such that there was more tissue destruction. than tissue repair, and that stenosis would result if there was more tissue repair than tissue destruction

Adult↗
PubMed1977

Transabdominal suture of bleeding gastro-oesophageal varices in cryptogenic cirrhosis of the liver.

Emergency transabdominal suture of gastro-oesophageal varices was performed when conventional conservative measures including oesophageal tamponade failed to control bleeding in 60 of 167 patients with cryptogenic cirrhosis and bleeding varices. The immediate mortality for the whole series was 29-9 per cent. Surgery performed in this selected manner carried an immediate mortality of 40 per cent. The transabdominal approach detected and treated 19 (31-7 per cent) patients who had concomitant bleeding from extra-oesophageal sources. Ageing and sex (male) affect the immediate prognosis adversely. Using a modification of Child's classification of hepatic dysfunction, a direct relationship between hepatic dysfunction and mortality was found, reaching 100 per cent in those with grade C (severe) dysfunction, irrespective of whether or not surgery had been performed. Bleeding was successfully arrested in 96-7 per cent of cases and recurrence of bleeding was acceptably low in the first 6 months of surgery but not after.

Adult↗
PubMed1977

Maximum acid output to graded doses of pentagastrin and its relation to parietal cell mass in Chinese patients with duodenal ulcer.

In groups of Chinese patients with duodenal ulcer and controls, increasing the dose of pentagastrin from the standard dose of 6 ug/kg or 12 ug/kg did not result in any change in the maximum acid output (MAO). Comparison of the MAO thus obtained with that reported in series of Occidental subjects suggested that the Chinese subjects had smaller MAO. Using the method of Card and Marks (1960), the parietal cells of resected stomachs were counted in a group of Chinese patients with duodenal ulcer. It was found that the parietal cell mass (PCM) correlated with the MAO, both PCM and MAO were significantly small in the Chinese series as compared with the Scottish series, but the acid output per unit parietal cell mass (MAO per 10(9) parietal cells) was not different in the two groups. These observations suggested that the Chinese patients with duodenal ulcer had smaller parietal cell mass compared with the Westerners.

Adult↗