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Biomedical subjects

K C Ng

Publications and source records attributed to K C Ng.

At least 55 records · Page 3Linked to original sources

The determination of short-term breast volume changes and the rate of synthesis of human milk using computerized breast measurement.

The feasibility of using sequential breast volume measurements as a method of studying short-term rates of milk synthesis in women has been established. We have developed a rapid Computerized Breast Measurement system for the determination of breast volume, based upon the Shape Measurement System. A circle encompassing all the breast tissue is drawn in black face paint on the subject's skin. Six patterns of sixty-four horizontal light stripes are projected onto the breast and chest wall surface. A CCD camera relays video images to a computer, which produces a model of the chest by active triangulation. The volume of the breast and the chest wall segment enclosed by the circle is then calculated. The precision of the method was dependent upon the subject repositioning carefully. The coefficient of variation of replicate measurements was 1.6%. The accuracy of the method was established by comparing the change in breast volume before and after a breast-feed with the amount of milk removed by the infant as determined by test weighing. There was a close relationship between the removal of milk by the infant (x) and the change in breast volume (y), (r = 0.93, n = 73, y = 1.10x - 3.25). The rates of milk synthesis between breast-feeds, for six women determined on one to eight occasions, varied from 11 to 58 ml/h. The results show that the amount of milk available in the breast is not necessarily an important determinant of the amount of milk removed by the infant at a breast-feed.

Breast↗

Clear cell chondrosarcoma--a report of 2 cases.

Clear cell chondrosarcoma is a form of chondrosarcoma that was first described by Unni in 1976. It is essentially a low-grade chondrosarcoma with many similar clinical, radiological and histological features as the more common chondrosarcomas. However, the distinguishing feature of this variant is in the presence of the characteristic clear cells histologically. We relate two such cases of clear cell chondrosarcoma in Singapore. A short discussion covering the incidence/prevalence of this tumour, its common presenting clinical, radiological and histological features follows. We also review the available world literature, highlight the salient and differentiating aspects of this particular tumour, and touch on its management and eventual prognosis.

Adult↗

Axillary artery damage from shoulder trauma--a report of 2 cases.

Various shoulder injuries can give rise to axillary artery complications. Two such cases were admitted to Tan Tock Seng Hospital late last year. Both were young adult males, who had developed axillary artery thrombosis secondary to shoulder injuries. The following is a short discussion on the common types of shoulder injuries, how they result in axillary artery compromise and a short section on their management and treatment.

Adult↗

Monte Carlo estimation of the electric field in stellarators.

The BETA computer codes have been developed to study ideal magnetohydrodynamic equilibrium and stability of stellarators and to calculate neoclassical transport for electrons as well as ions by the Monte Carlo method. In this paper a numerical procedure is presented to select resonant terms in the electric potential so that the distribution functions and confinement times of the ions and electrons become indistinguishable.

Journal Article↗

Computer-controlled muscle paralysis with atracurium in the sheep.

Paralysis was maintained in sheep by computer-controlled infusion of atracurium, using the integrated electromyogram as a measure of neuromuscular transmission. A number of experiments were conducted to ascertain the average infusion rate required to achieve a given level of paralysis for one hour. Each experiment yielded a point on a plot of paralysis versus infusion rate. A dose-response curve based upon a simple model of drug receptor interaction at the neuromuscular junction was fitted to the experimental points by least squares and is able to provide a useful explanation of clinically observed behaviour. The recovery time was also measured in each experiment and plotted against both prior level of paralysis and prior average infusion rate.

Animals↗

Incidence of metabolic bone disease in rheumatoid arthritis and osteoarthritis.

Bone biopsy specimens from the iliac crest were obtained during surgical operations from 45 patients with rheumatoid arthritis (RA) and 41 with osteoarthritis (OA). Control material was obtained from 20 cases of sudden death due to cardiovascular disease. By both conventional histology and image analysis techniques about a quarter of all patients showed some osteoporosis. This was equally common among the OA and RA patients. It was more common among those with transparent skin and those taking corticosteroids. The only case showing mild osteomalacia suffered from OA. No gross differences were apparent between the groups in relation to plasma biochemical studies, diet, or exposure to sunlight. These results are in striking contrast to the high incidence of osteomalacia in RA reported from the west of England; moreover they do not confirm reports of hypercalcaemia among rheumatoid subjects. We conclude that the differences regarding osteomalacia are due to selection of cases. We find no evidence that osteomalacia is specifically associated with RA.

Aged↗

Factors influencing the autologous mixed leukocyte reaction in normal subjects.

The proliferative response of T cells to autologous non-T cells (autologous mixed leukocyte reaction, AMLR) varies with the duration of incubation as well as the concentration and nature of the stimulator cells. The peak response was generally found on days 6, 7 or 8 of incubation, but with unseparated non-T cells, as well as varying in different individuals this varied in the same individual on different days. Removal of adherent cells from the stimulator population increased the magnitude of the peak response and improved day-to-day consistency both in size of peak response and in the duration of incubation required. Adherent cells were poor stimulators. Some of the variability in AMLR in normals and the differences between normal and disease subjects may relate to inclusion of an adherent cell population in the test and to the use of a fixed time period for incubation.

Cell Adhesion↗

Electromyographic monitoring of neuromuscular block.

Neuromuscular blocking agents are widely used in anaesthesia, and a simple quantitative method of monitoring their effects is desirable. This paper describes a new instrument which has been developed for electromyographic monitoring of neuromuscular block by a non-invasive technique which is both reliable and easy to use. The median nerve is stimulated at the wrist and the electromyogram (e.m.g.) from a thenar muscle is detected, rectified and integrated electronically to produce a meter display of the assessment of block. The method is recommended for routine use.

Child↗

Anti-RANA antibody: a marker for seronegative and seropositive rheumatoid arthritis.

Without prior knowledge of the diagnosis or clinical status, sera from patients with various arthritides were screened for antibody against rheumatoid-arthritis-associated nuclear antigen (RANA) with indirect immunofluorescence on cytocentrifuged Raji cell preparations. 93% of 103 seropositive rheumatoid patients had anti-RANA antibody, in contrast to 16% of 50 normal controls and a mean of 19% (10-29%) of 122 patients with other arthritides. Anti-RANA antibody was also demonstrated in 95% of 21 patients with seronegative rheumatoid arthritis characterised by symmetrical erosive peripheral polyarthritis. No correlation was found in rheumatoid arthritis between anti-RANA antibody and disease activity, duration of disease, drug therapy, or extra-articular manifestations. RANA staining was absent in a non-Epstein-Barr-virus (EBV) cell line (Ramos). In 10 rheumatoid patients, discordance between the presence of antibodies to EBV antigens (viral capsid antigen [VCA] and EBNA) ANd RANA antibody was demonstrated. Anti-RANA antibody could be a useful marker for rheumatoid arthritis.

Antibodies, Antinuclear↗

Denaturation of DNA in the presence of chromous (Cr2+) ions.

The effect of Cr2+ ions on the Tm (melting temperature) of DNA has been investigated under appropriate conditions for the stabilization of DNA by Mg2+ ions. A significant lowering of Tm, analogous to that observed for Cu2+ under normal conditions, was found, for Cr2+ at pH = 4.2 and [Mg2+] = 5.3 mol per mole of DNA base pair. Cu2+ also lowers Tm under similar conditions. The similarity of the effects of Cr2+ and Cu2+ under comparable conditions may be related to similarities in their coordination properties. It is proposed that Cr2+ and Cu2+ ions facilitate denaturation by holding together groups on the DNA chains in such a manner that base pairing and base stacking are inhibited. Comparative results for Cr3+ and Co2+ are also given for these low pH/Mg2+ ion conditions.

Animals↗

Dosage patterns of non-depolarizing neuromuscular blockers in the sheep.

Eighty per cent paralysis was induced and maintained for 90 minute in the sheep by computer-controlled injection of gallamine, pancuronium, alcuronium or d-tubocurarine, using the integrated electromyogram as a measure of neuromuscular transmission. The dosage pattern consisted of a loading phase before any IEMG depression was detected, an onset phase during which a moderate amount of drug was required to achieve increasing paralysis, and a maintenance phase during which a substantially constant and relatively low infusion rate was required. The steady state rates of infusion in microgram/kg/min during "maintenance" was found to be 6.0 for gallamine, 0.15 for pancuronium, 0.2 for alcuronium and 0.5 for d-tubocurarine.

Alcuronium↗

Reversal of non-depolarizing block by neostigmine.

Paralysis was maintained in the sheep for 30 or 90 minutes by computer-controlled injection of gallamine, pancuronium, alcuronium or d-tubocurarine, using the integrated electromyogram as a measure of neuromuscular transmission. Neostigmine was given and the recovery time measured. In all trials the recovery rise time was no longer than two minutes, but varied between one and two minutes.

Animals↗

Unusual small intestinal obstruction in adolescent girls: the abdominal cocoon.

Ten cases of small intestinal obstruction seen over a period of 6 years (1971-6) in young girls within the narrow age range of 13-18 years are described. The patients were all within 2 years of menarche. In all these cases the obstruction was due to a membrane encasing the small intestine in the manner of a cocoon. There was no previous history of abdominal operation, peritonitis or prolonged drug intake. The clinical features, operative findings and management of the cases are presented. Possible causes of the condition are discussed. In view of the similar clinical presentation in all these patients, their conditions can be grouped as a clinical entity--'the abdominal cocoon'.

Adolescent↗