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Biomedical subjects

S T Chan

Publications and source records attributed to S T Chan.

At least 91 records · Page 5Linked to original sources
PubMed1989

Hypaque and steroids in the treatment of sudden sensorineural hearing loss.

While the origins of sudden sensorineural hearing loss remain unproven and treatment empirical, the most appropriate therapy remains a matter of controversy. In this paper we have analysed the current forms of treatment, i.e. diatrizoate meglumine, steroids and a vasodilator. The results suggest that although several related factors were shown to indicate a good prognosis regardless of the therapy, none of the currently available regimens produces consistently better results than the spontaneous recovery rate of 65% reported by Mattox & Simmons.

Adult↗
PubMed1989

Choriocarcinoma following term pregnancy--a case report.

A patient, with two previous term deliveries, presented with post-partum haemorrhage and spontaneous uterine perforation due to choriocarcinoma, requiring emergency laparotomy. Choriocarcinoma following term pregnancy is a rare form of gestational trophoblastic disease. Such tumour appears to follow a more aggressive course with a more extensive metastatic spread and is less responsive to chemotherapy resulting in a poorer prognosis. Choriocarcinoma presenting as postpartum haemorrhage, and spontaneous tumour perforation with intra-abdominal haemorrhage is even rarer. Early diagnosis is an important factor for the patient's survival. A high index of suspicion is required as the tumour may be overlooked. An aggressive chemotherapeutic regime has improved the overall survival.

Choriocarcinoma↗
PubMed1988

Zinc amelioration of cadmium toxicity on preimplantation mouse zygotes in vitro.

Zinc, at a concentration of 5 or 10 micrograms/ml medium, has been shown to protect mouse preembryos in vitro from the toxicity of cadmium at a concentration of 5 micrograms/ml medium after a simultaneous treatment of the ions from four-cell to morula or from morula to blastocyst for 24 hours. Such an amelioration indicates that cadmium toxicity is a result of the unique property of the cadmium ion and is not due to an alteration in the culture medium after the addition of an extra metallic ion. Zinc probably ameliorates cadmium-treated mouse preembryo by competing with cadmium for uptake or some other metabolic processes. In view of the well-documented competition between cadmium and zinc ions for binding sites in many other cell types, some macromolecules to which similar divalent metallic ions bind competitively may also exist in the mouse preembryo. This suggests that a protective mechanism dependent on the metal-metal interactions begins to operate in the mouse preembryo at a very early stage of differentiation before implantation.

Animals↗
PubMed1988

Arteriovenous malformation in children.

A retrospective study was carried out on 39 patients, all under the age of 16, who suffered from intracerebral arteriovenous malformation (AVM). All had unilateral lesions except for 1 who had bilateral AVMs. The incidence, age, sex distribution, and symptomatology are discussed. Surgical extirpation was carried out if possible after assessment by angiography and computed tomography. Inoperable cases were managed conservatively and followed up. The possibility that AVMs grow was demonstrated. Based on the promising results of the cases operated upon, it is strongly believed that total surgical excision is the treatment of choice. The importance of a microsurgical approach is stressed.

Adolescent↗
PubMed1988

Dural arteriovenous malformation presenting as cardiac failure in a neonate.

Dural arteriovenous malformation (AVM) is a rare clinical entity, presenting most commonly in adult patient with pulsatile tinnitus or haemorrhage. We report a case of a neonate with a massive dural arteriovenous malformation (AVM) with signs of cardiac failure soon after birth. The diagnosis was first suggested during angiocardiography when a hypertrophied left common carotid artery was detected. The AVM was supplied by branches from the left external carotid artery and the left veretebral artery and drained into the left transverse sinus near the torcula. This was excised in two stages. Post-operative angiography showed no residual malformation. The patient was well and developing normally 4 years after surgery. Review of the literature showed only 2 similar cases of dural AVM presenting in the neonatal period, both patients died, reflecting the high risks involved and the difficulties encountered in the management. Ligation of arterial supplies can be a useful temporary procedure in these high risk babies. Definitive excision should be performed later when the baby grows stronger.

Carotid Arteries↗
PubMed1988

A technique of undermining a V-Y subcutaneous island flap to maximise advancement.

A method is described where the planned directional undermining of a subcutaneous triangular flap creates a long pedicle and in the process the flap is "unfolded" to increase its advancement. The flap can be undermined and advanced without any tension. This method is recommended where more conservative undermining is inadequate for mobilisation, particularly in larger defects and in the replacement of skin defects on the lower eyelid which needs to support the eyelid. This technique depends on the richness of the random blood supply in the head and neck regions and the availability of adequate depth of subcutaneous tissue for the development of a long pedicle. Using this method in 53 cases, it has been found possible to advance the flap way past the defect if so desired. Some minor disadvantages of this flap are also described.

Adult↗
PubMed1988

Cadmium toxicity on mouse pre-implantation zygotes in vitro: interactions of cadmium with manganese, zinc and calcium ions.

Simultaneous treatment with cadmium chloride (5 micrograms/ml medium) and manganese chloride (5 or 10 micrograms/ml medium) was less toxic to mouse pre-implantation zygotes in vitro than cadmium alone. Such a protective effect of manganese, resembling that of zinc, suggests that amelioration of cadmium-treated pre-embryos in vitro is not unique to zinc. The amelioration may require only the presence of another divalent metallic ion, such as zinc or manganese, which is capable of competing with cadmium for binding sites possibly involved in uptake. Under calcium-free conditions cadmium embryotoxicity is enhanced, showing a summation effect of the cadmium toxicity and the lack of calcium. This supports the notion that excessive exogenous calcium may render the effects of cadmium on compaction inconspicuous. The non-compacted pre-embryos treated with 5 micrograms/ml cadmium in a calcium-free medium had fewer blastomeres than those treated at a lower dose of 1 microgram/ml. Cadmium appeared to inhibit the cleavage from 8-cell to 16-cell stage, but not from 4-cell to 8-cell.

Animals↗
PubMed1987

The plasma sex steroid profiles in the freshwater, sex-reversing teleost fish, Monopterus albus (Zuiew).

The plasma levels of both the free and conjugated forms of six sex steroids (androstenedione, testosterone, 11-oxotestosterone, 11 beta-hydroxytestosterone, estrone, and 17 beta-estradiol) were determined by radioimmunoassay combined with Celite chromatography in different sexual phases of the protogynous Monopterus albus throughout the reproductive cycle. The amounts of 11-oxotestosterone and 11 beta-hydroxytestosterone were found to be very low and variable in all the specimens investigated. No conjugated 17 beta-estradiol or free estrone was detected. Female individuals showed a prespawning rise of androstenedione which subsequently dropped to a low level in the spawning period. The estrogen levels in the female phase were found to be higher than those in all other sexual phases during the spawning period, but the testosterone level remained constant throughout the reproductive cycle in the female phase. The level of androstenedione was highest in the early intersexual and mid-intersexual phases during the postspawning/inactive period. Compared with the female specimens in the same reproductive period, the early intersexual individuals showed a higher level of 17 beta-estradiol, while the mid-intersexual animals showed a higher level of testosterone in the postspawned/inactive period. In the mid-intersexual phase, the levels of androstenedione, testosterone, 17 beta-estradiol, and estrone dropped progressively in relation to the seasonal reproductive cycle. The male fish had a constant level of androstenedione, estrone, and 17 beta-estradiol. However, the level of testosterone increased as the spawning period approached. The hormonal profile in the late intersexual phase was essentially similar to that in the male phase. The changes in the plasma levels of sex steroids in M. albus apparently were related to the maturation of the female and male sex tissues and to their seasonal reproductive cycle.

Androstenedione↗
PubMed1987

A radioimmunoassay study of the plasma levels of sex steroids in the protandrous, sex-reversing fish Rhabdosargus sarba (Sparidae).

By Celite chromatography and radioimmunoassay, the levels of free and conjugated forms of androstenedione, testosterone, 11-oxotestosterone, 11 beta-hydroxytestosterone, 17 beta-estradiol, and estrone have been determined in the plasma of the protandrous sex-reversing Rhabdosargus sarba at different sexual phases throughout the seasonal reproductive cycle. Free androstenedione showed a significant increase during the spawning period in the functional male phase, while a prespawning increase in both the free and the conjugated androstenedione was found in the female phase. The level of testosterone remained fairly constant throughout the reproductive cycle in all sexual phases except the intersexual phase, which was found to have a slight increase in the free testosterone level during the spawning period. Females showed a prespawning increase in free 17 beta-estradiol and conjugated estrone; the former dropped while the latter remained unchanged in the succeeding spawning period. A prespawning rise of conjugated 17 beta-estradiol was also found in the male specimens. The level of free estrone was undetectable in the plasma of Rhabdosargus. No variation in the levels of 11-oxotestosterone and 11 beta-hydroxytestosterone was found in the different sexual phases throughout the reproductive cycle. The present study showed that in general the steroid patterns in the male and intersexual phases were basically similar, except perhaps that the levels of conjugated 17 beta-estradiol, conjugated androstenedione, and free testosterone were slightly higher in the intersex than in the male during the spawning period. The changes in the plasma levels of sex steroids were correlated with the structural transformation in the gonad and the seasonal cycle of the fish. The results were analyzed with special references to the phenomenon of natural sex reversal and to the endocrine patterns known in other teleost fishes.

Androstenedione↗
PubMed1987

Microcomputer system for the analysis of muscle function.

Though skeletal muscle function has recently been increasingly studied, a system for routine clinical examination in patients is not widely available. A microcomputer based system has been developed for the measurement and analysis of force-frequency characteristics, relaxation rate, fatiguability and endurance in the adductor pollicis muscle. The mobile system consists of a modified displacement transducer fitted with a linear-output Hall-effect sensor, a specially designed signal processing unit and a microcomputer for control of both the electrical stimulus and a suite of menu-driven, user-interactive programs. One hundred normal volunteers have been studied to produce a normal database for comparison with malnourished surgical patients. The system compares favourably with other systems in use for objective measurement of skeletal muscle function and introduces a refined technique for evaluating endurance.

Biomedical Engineering↗
PubMed1987

Effects of cadmium on preimplantation and early postimplantation mouse embryos in vitro with special reference to their trophoblastic invasiveness.

Cadmium chloride, at concentrations of 0.5 or 1 microgram/ml medium, did not affect the trophoblastic invasiveness of mouse embryos treated for 24 hours at 4-cell and morula stages. At higher concentrations of 5 or 10 micrograms/ml medium, most treated embryos in vitro underwent degeneration while a few survivors formed trophoblastic outgrowths with variable areas. Cadmium chloride, at a low concentration of 0.5 microgram/ml medium presented continuously to blastocysts after attachment in vitro, has significantly retarded the trophoblastic outgrowth areas and reduced the number of trophoblastic giant-cell nuclei, though the spreading blastocysts appeared morphologically normal. At higher concentrations of 1 or 5 micrograms/ml medium, cytoplasmic disintegration and detachment of trophoblasts were observed. It is suggested that cadmium may interfere with the cell division and/or the transformation of trophectoderm cells into giant cells, resulting in the retardation of the trophoblastic outgrowths.

Animals↗
PubMed1987

Sparganosis of the brain. Report of two cases.

Cerebral sparganosis is a rare disease; to date only eight cases have been described. Two new cases of cerebral sparganosis occurring in Chinese patients living in a metropolitan area are reported. Their clinical presentation and investigative results are presented and the operative and histological findings detailed. A brief review of the condition is given and the possible source of infection discussed.

Brain Diseases↗
PubMed1987

Early versus delayed cholecystectomy for acute cholecystitis.

The controversy between early or delayed cholecystectomy continues, although recent opinion appears to favour the early approach. If this policy of early operation is to be adopted then an accurate diagnosis must be obtained at the earliest opportunity. An accurate diagnosis of acute cholecystitis is made from a careful history, the relevent clinical findings and if possible a HIDA scan demonstrating non-filling of the gallbladder. However, if radionucleotide scanning is not available then real-time ultrasonography is the next best choice, but must be interpreted with care as it is not as specific as the HIDA scan. The advantages of removing the disease process at one hospital admission are considerable, and result in a substantial saving of days spent in hospital, without the problem of patients developing recurrent symptoms while waiting for a delayed cholecystectomy. The operation is occasionally technically demanding, but this can equally well be the case when a delayed cholecystectomy is performed. If the surgeon finds that the acute inflammation is so severe that structures around Calot's triangle cannot be safely dissected then the surgeon must be prepared to retreat and perform a cholecystostomy (Skillings et al, 1980). If the delayed approach is followed, then the patient must be re-examined at regular intervals.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1986

Muscle power after glucose-potassium loading in undernourished patients.

The force-frequency characteristics and maximal relaxation rate of the adductor pollicis muscle were measured before and after 48 hours of intravenous loading with glucose (104.5 kJ (25 kcal)/kg/24 h) and potassium (20 mmol(mEq)/500 ml glucose) in eight undernourished patients about to undergo surgery. Both variables of skeletal muscle performance, which were depressed when compared with data from 100 healthy volunteers, improved significantly after glucose-potassium loading. The improvement was accompanied by restoration of muscle glycogen values and return of respiratory exchange ratios towards unity. These results imply that if muscle power is a yardstick for preoperative nutritional rehabilitation then a simple regimen of energy-electrolyte repletion may be cost effective in preparing undernourished patients for major surgery.

Glucose↗
PubMed1986

Extended indications for polypropylene mesh closure of the abdominal wall.

Over a two-year period (1982-1984) polypropylene (Marlex) mesh was used without closing the abdominal wound in 21 patients judged clinically likely to require further abdominal exploration. A total of 43 meshes were implanted. All 21 patients had more than one major laparotomy, median 3 laparotomies (range 2-7) for drainage of pus (76 per cent) and/or intestinal leakage (67 per cent). Definitive abdominal wound closure after removal of polypropylene mesh was either by delayed primary suturing (33 per cent) or consisted of split skin grafting on the granulating wound (24 per cent). Three wounds were left to granulate without skin grafting (14 per cent). Mortality in this group of patients was 29 per cent and no complications resulted directly from implantation of polypropylene mesh. Polypropylene mesh closure of the abdominal wall not only provides simple and rapid access to the abdomen but also allows free drainage and daily inspection for the development of fistulae or the seepage of pus which are indications for further exploration. In that the clinical outcome is relatively favourable in this group of critically ill surgical patients who required multiple laparotomies within a short interval, it is suggested that mesh closure of the abdominal wound is indicated whenever abdominal re-entry is judged probable or rational.

Abdominal Muscles↗
PubMed1986

Effects of cadmium on lactate dehydrogenase activities in mouse pre-embryos at various stages.

A decline in LDH activity from four-cell to late blastocyst was demonstrated in pre-embryos from F1 (C57 female X A2G male) female mice. An exposure to 0.5 or 1 microgram/ml cadmium did not affect the in vitro development of the four-cell pre-embryos and morulae or their LDH activities. At 5 or 10 micrograms/ml cadmium, the in vitro development of the treated pre-embryos was affected. Although most of the treated four-cell pre-embryos had proceeded to compaction, they became degenerated 24 h after treatment. The LDH activity of these degenerated pre-embryos was higher than that in the control blastocysts. We propose that cadmium may interfere with the general energy metabolism of the cells. This causes a reduced rate of LDH degradation, leading to a slower decline in LDH activity in cadmium-treated pre-embryos. Failure of some critical biochemical processes after cadmium treatment may ultimately lead to the subsequent degeneration of the treated pre-embryos.

Animals↗