Biomedical subjects
Publications and source records attributed to R C Chan.
In 1986 a study was made on the prevalence of cervical colonization by cytomegalovirus (CMV) in normal third trimester pregnant Chinese women in Hong Kong. Seven out of 95 unselected subjects had positive CMV culture, making a prevalence of 7.4%. This is a low prevalence when compared with the prevalence found in other people of Asian origin and similar to the prevalence found in the Caucasians.
The purpose of this study is to determine a data range of the surface area of compound muscle action potential (CMAP) in normal abductor pollicis brevis and abductor digiti minimi. 256 median nerves and 317 ulnar nerves which were proved to be normal by NCV and EMG studies were included. Computer-aided measurement of distal latency, amplitude and nerve conduction velocity plus author-designed negative surface area reading was done. The surface areas of different age groups ranged from 28.6 to 35.3 ms*mV in abductor pollicis brevis and 30.0 to 31.5 ms*mV in abductor digiti minimi. There is no significant difference between different ages and between both sexes. The surface area showed statistically significant correlation with amplitude but no correlation with distal latency and nerve conduction velocity. It is concluded that as the concept of surface area is widely accepted and the measurement technique is more easily available, to set up a normal data base of surface area of the routinely examined muscle is very important and the surface area of CMAP should be included into the interpretation of routine nerve conduction studies.
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The outcome of 93 consecutive cycles of in vitro fertilization (IVF) and embryo transfer (ET) treatment in 52 women with "frozen pelvis" is reported. The treatment termination rate due to inadequate ovarian stimulation was 20%. The mean +/- standard deviation of the number of follicles of mean diameter greater than or equal to 15 mm, oocytes recovered and fertilized per operation, and embryos replaced per cycle were 4.80 +/- 2.07, 4.02 +/- 2.32, 2.54 +/- 2.06, and 2.57 +/- 1.30, respectively. The pregnancy rate per ET was 29.6%. These data compare with those of other treated women with adhesion-free ovaries over the same period, suggesting that pelvic adhesive disease has no adverse effect on outcome of IVF-ET.
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This paper reports on the effects of an increase in size of the recording surface of monopolar needles on motor unit potentials (MUPs). The teflon coating of the TECA monopolar needles MG37 and MF37, commonly used in clinical electromyography, was progressively denuded to increase the length of the recording tip to 2, 3, 5, and 10 times the normal exposure, with resultant increase in the area of the recording portion. Low threshold MUPs obtained on minimal contraction from the tibialis anterior were analyzed for amplitude, duration, area, phases, turns, peak duration, and index. The amplitude and area of the MUP showed the most change, both decreasing with progressive denudation. The number of turns and phases were also reduced, more for the MF than for the MG needle. Duration, peak duration, and index showed insignificant changes. These findings give further support to the use of duration for representation of the MUP, since this is the most stable parameter even under poor recording conditions.
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A simple modification of the Salmonella liquid incubation assay previously developed for detecting mutagens in urine was used to determine mutagenic activity of airborne particulate matter. The modification consists of adding ten times more bacteria (approximately 10(9) per incubation tube) and five to ten times less metabolic enzymes compared to the plate incorporation method. The mixture volume is approximately 0.2 ml, and the mixture is incubated for 90 min before pouring it according to the standard protocol. The modified procedure (micro preincubation or microsuspension) was approximately ten times more sensitive than the standard plate incorporation test for detecting mutagens in air particulate extracts and approximately ten to 31 times more sensitive for the chemical mutagens 2-nitrofluorene, 4-nitroquinoline-N-oxide, 2-aminofluorene, and benzo(a)pyrene in bacterial strain TA98. Mutagenic activity was detected in particle extracts obtained from 1 m3 of air (17 micrograms of extract) or less. This microsuspension procedure was applied to air particulate samples collected with low-volume (15-50 liters per min) virtual-dichotomous air samplers. Mutagenic activity was associated exclusively with fine particles (aerodynamic diameters of less than 2.5 microns). Diurnal patterns of mutagenic activity (TA98 revertants per cubic meter air) were investigated by measuring filter extracts from 2-hr samples collected in three San Francisco Bay Area cities during the summer or fall of 1982. Four criteria pollutants--lead, nitrogen dioxide, ozone, and sulfur dioxide--were simultaneously sampled at one location. Mutagenicity from fine particles sampled at this location was highly correlated with lead and much less correlated with nitrogen dioxide, ozone, and sulfur dioxide. The microsuspension procedure is applicable in testing samples of limited mass.
In primary cultures of ovine thyroid cells, TSH induced the expression of several differentiated functions including the formation of follicles, and synthesis and storage of iodinated thyroglobulin in the follicular lumen. In the present report, these follicles were shown by transmission (TEM) and scanning electron microscopy (SEM) to be intact, comprised of two or more cells and to possess numerous microvilli on the inner cell membranes facing the follicular lumen. The TSH-induced formation of follicles was reversible and dynamic, with the kinetics of formation preceding that of iodination. The follicles were further demonstrated to be functional in terms of thyroglobulin storage and iodination.
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Previous studies have shown that indigenous bacteria isolated from cervical, vaginal, and urethral surfaces of healthy women are able to adhere to human uroepithelial cells in vitro. Furthermore, these organisms were found to block the adherence of uropathogenic bacteria to uroepithelial cells from women with and without a history of urinary tract infections. In the present study, complete or partial inhibition of the adherence of gram-negative uropathogens was achieved by preincubating the uroepithelial cells with bacterial cell wall fragments isolated from a Lactobacillus strain. Competitive exclusion was most effective with whole viable cells and less effective with cell wall fragments obtained by sonication, extraction with sodium dodecyl sulfate, and treatment with sodium dodecyl sulfate and acid. Analysis of the Lactobacillus cell wall preparations suggested that lipoteichoic acid was responsible for the adherence of the Lactobacillus cells to uroepithelial cells but that steric hindrance was the major factor in preventing the adherence of uropathogens. This conclusion was also supported by blockage studies with reconstituted lipoteichoic acid-peptidoglycan, which was more effective at blocking adherence than lipoteichoic acid or peptidoglycan alone. The results suggest that the normal flora of the urinary tract may be used to protect against the attachment of uropathogens to the surfaces of uroepithelial cells. The long-term implications of these findings may lead to alternative methods for the management and prevention of recurrent urinary tract infections in females.
Our previous studies have shown that indigenous bacteria are able to block the in vitro attachment of uropathogenic bacteria to human uroepithelial cells. In the present study, we applied the concept of competitive exclusion to an animal model. A chronic urinary tract infection was established in female rats with bacteria incorporated into agar beads injected periurethrally into the urinary bladder via a no. 3 French ureteral catheter. Five strains of uropathogenic organisms were used in the first set of experiments, and their colonization of the bladder and kidneys of the animals was confirmed up to 2 months after injection. The uropathogens stimulated an immune response, detected by serum antibodies against the uropathogens, and an inflammatory response noted in sections of the kidneys stained with hematoxylin and eosin. Using this animal model, we established the persistent adherence of bacteria in the urinary tract without the need for creation of obstruction or implantation of a foreign body. In a second set of experiments, an isolate of Lactobacillus casei GR1 taken from the urethra of a healthy woman was incorporated into agar beads, instilled within the rat bladders on day 1, and then swabbed twice weekly for 21 days onto the introitus before challenge with uropathogens instilled into the urinary bladder. In 21 of 25 animals, no uropathogenic bacteria were recovered from the bladder and kidney tissues up to 60 days after challenge, and no immune response was detected. Our results show that L. casei prevented onset of urinary tract infection in 84% of the animals tested. The lactobacilli appeared to exclude the uropathogens from colonizing the urinary tract, within the first 48 hours after challenge, and the net effect was a complete eradication of bacteria from the uroepithelium. It is hoped that the demonstration of a protective role for indigenous bacteria in preventing urinary tract infection in an animal model will lead to the application of this technology to prevent recurrent urinary tract infection in female patients.
The authors report a case of symptomatic arachnoid diverticulum, which was located anterior to the spinal cord and covered the entire length of the spinal canal. The patient underwent cervical laminectomy and cystoperitoneal shunting with subsequent neurological improvement. The causes, clinical manifestations, diagnosis, and management of spinal arachnoid diverticulum are discussed.
We reviewed the case histories of 350 patients who were diagnosed as having intracranial meningeal tumor between 1960 and 1981. Of these, four patients (1.1%) had meningiomas during childhood. The patients were two boys and two girls, and postoperative observation ranged from 6.5 to 38.5 years. All four patients presented with seizures. In three out of four patients, the tumors were located in the convexity regions; the other was intraventricular. One of the four tumors demonstrated histologic malignancy, and the patient subsequently died; radiation therapy may have prolonged the survival of this particular child, however. The other three children with benign meningeal tumors have all enjoyed good-quality, long-term survival since the excisions of their tumors and the tumors' dural attachments.
A retrospective study of 50 patients with urinary diversion was undertaken to determine the incidence of bacteriuria and upper tract infection. Eighty-four per cent of these patients developed bacteriuria caused by a variety of pathogenic organisms and 14 per cent had clinical evidence of pyelonephritis. A phased morphological and bacteriological study was then carried out in a further 17 patients with ileal conduits. Electron microscopy examination of cup biopsy specimens from superficial and deep segments of the conduit showed virtually no bacteria adhering to the columnar cells of the conduit, although Gram positive cocci were seen adhering to the keratinized cells from the muco-cutaneous junction. However, the conduit mucus was heavily colonized, initially with yeasts, then sequentially with microcolonies of Gram-positive and Gram-negative bacteria, up to 16 years after urinary diversion had been performed. Bacteriological examination of conduit and stomal mucus and urine specimens of these 17 patients confirmed the presence of large numbers of uropathogens . Of 23 conduit isolates, 9 possessed hemagglutinins, 18 of 18 attached to uroepithelial cells in vitro and 6 of 6 attached to ureteral transitional cells in vitro, indicating their adhesive and pathogenic capabilities.