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Biomedical subjects

S Lam

Publications and source records attributed to S Lam.

At least 181 records · Page 10Linked to original sources
PubMed1984

Deep venous thrombosis: detection by high-resolution real-time ultrasonography.

High-resolution real-time ultrasonography was performed in 11 patients with clinically suspected deep venous thrombosis (DVT) of the lower extremity. Contrast venography was performed in all patients within 24 hours of sonographic examination. The common femoral vein at the groin and the popliteal vein in the popliteal fossa were evaluated for presence or absence of intraluminal soft-tissue mass (thrombi), compressibility of the veins, and response to performance of the Valsalva maneuver. Of the 11 patients, six were shown to have DVT by contrast venography. In all six cases there was complete agreement between sonography and contrast venography as to the presence or absence of thrombi in the common femoral vein or the popliteal vein.

Adolescent↗
PubMed1984

A biophysical, morphological and morphometrical survey of the eye of the small shark (Hemiscyllium plagiosum).

The biophysical and morphological characteristics of the small shark's ( Hemiscyllium plagiosum ) eye were studied. The focal lengths of the lens were found to be very short. A small proportion of cones were present in the retina and this proportion varied with the weights of the sharks. The topographic distribution of cones in different segments of the retina was also presented.

Animals↗
PubMed1983

Relationship between types of asthmatic reaction, nonspecific bronchial reactivity, and specific IgE antibodies in patients with red cedar asthma.

We studied the relationship between specific IgE antibodies, nonspecific bronchial reactivity to methacholine, and the type of asthmatic reaction in patients with red cedar asthma. The level of circulating specific IgE antibodies (expressed as RAST ratios) was not related to the type of asthmatic reaction, the degree of nonspecific bronchial hyperreactivity [expressed by the provocative concentration of methacholine producing a 20% decrease in the forced expiratory volume in 1 sec (PC20)] or the index of reactivity to plicatic acid. On the other hand, methacholine PC20 was found to correlate with the index of reactivity to plicatic acid in the late asthmatic reaction (LAR) and both the immediate and late components of the dual asthmatic reaction (DAR). Development of the LAR is associated with increase in nonspecific bronchial hyperreactivity. Repeated inhalation challenge with plicatic acid in eight patients with LAR resulted in DAR in all. The results suggest that the mechanism responsible for the LAR is associated with an increase in nonspecific bronchial reactivity; furthermore, the immediate component of DAR could also be related to heightened bronchial hyperreactivity.

Adult↗
PubMed1983

IS200: a Salmonella-specific insertion sequence.

A new IS element (IS200) has been identified in Salmonella. The sequence was identified as an IS element by the following criteria: its insertion caused the mutation hisD984; six copies of the sequence are present in strain LT2 of S. typhimurium; and transposition of the sequence has been observed on several occasions. IS200 is found in almost all Salmonella species examined but is absent from most other enteric bacteria. The specificity of this element for Salmonella (and the absence of IS1-IS4 from Salmonella) suggest that transfer of insertion sequences between bacterial groups may be less extensive than is commonly believed. Alternatively, the distribution may suggest that these elements play a selectively important role in bacteria.

Base Sequence↗
PubMed1983

Genetic mapping of IS200 copies in Salmonella typhimurim strain LT2.

The wild-type Salmonella typhimurium strain LT2 contains six copies of the insertion sequence element IS200 which is unique to Salmonella. We have determined the chromosomal locations of all six copies of IS200 in strain LT2. This was done by mapping the positions of Tn10 elements inserted near each copy of IS200. Such Tn10 insertions were detected by Southern hybridization as IS200-containing restriction fragments with altered electrophoretic mobility. The copies are located at quite evenly spaced sites in the chromosome. Some are found in regions with many known genes; others are in regions with few known functions. There is no indication of a possible function for IS200. The method described here should be applicable to the mapping of IS elements in general.

Chromosome Mapping↗
PubMed1982

Clinical features and natural history of occupational asthma due to western red cedar (Thuja plicata).

After an average follow-up interval of three and a half years (range one to nine years), 125 patients with occupational asthma due to red cedar exposure were re-examined. Fifty patients remained in the same job. All of them continued to have asthmatic attacks requiring regular medication for relief of symptoms. They had worse lung function and ther bronchial reactivity to methacholine increased. Seventy-five patients left the industry; half of them became asymptomatic, whereas the remaining half continued to have recurrent attacks of asthma. Several factors were of prognostic significance. Those with a shorter duration of exposure as well as a shorter duration of symptoms prior to diagnosis and removal from exposure showed improvement. Those who remained symptomatic tended to be older; they had longer duration of exposure and a longer duration of symptoms prior to diagnosis. They tended to have more abnormal results of lung function studied and more marked bronchial hyper-reactivity to methacholine at the time of diagnosis. They also tended to have dual asthmatic reaction rather than late asthmatic reaction to inhalation challenge with red cedar extract. Smoking, race and degree of peripheral blood eosinophilia did not play a role in determining the outcome. Since none of these patients had symptomatic asthma before employment and since they reacted to inhalation challenge of red cedar, it could be assumed that persistent asthma in those who failed to recover is the result of their previous occupational exposure. Early diagnosis and removal from exposure were found to be associated with recovery.

Adult↗
PubMed1982

Computed tomography of pressure sores, pelvic abscess, and osteomyelitis in patients with spinal cord injury.

Nine patients with spinal cord injury (SCI) and large pressure ulcers and other possible complications, were evaluated by computed tomography (CT), conventional radiography, tomography, bone scanning, gallium scanning, and sonography. CT revealed the depth, extent, and relationship of the ulcer-bed to the underlying structures in all 9 patients. CT also positively identified unsuspected intra- and extra-pelvic abscess and pelvic osteomyelitis in 4 patients each. Other modalities identified only 2 of these complications. We believe CT is the modality of choice for evaluation of these complications in SCI patients, because of its superior ability in evaluation of pressure sores and detection of pathologic changes in soft tissue and bone in the pelvic region.

Abscess↗
PubMed1981

Therapeutic drug assays with gas-liquid chromatography and optical detection.

Clofibric acid (p-chlorophenoxyisobutyric acid), the major metabolite of Clofibrate, a drug used in the treatment of hyperlipemia, was assayed in blood serum using an ultraviolet absorbance monitor as a gas-liquid chromatographic detector. As in other gas-liquid chromatographic assays for this compound, an internal standard, p-chlorophenoxyacetic acid, was added, and the serum was acidified and extracted with organic solvent. The solvent was then evaporated and the acids converted into their methyl esters for analysis. The organic compounds in the effluent were scrubbed into a stream of 2-propanol, at a flow-rate of 0.5 ml/min. This was then "debubbled" and a portion drawn through the 20-microliters UV detector flow cell. With small-volume scubber and associated components, peak-broadening was minimal. Because of their moderately high extinction coefficients at 280 nm, the Clofibrate and the internal standard were detected in the submicrogram range without interference from long-chain fatty acid esters, which have similar retention times on the column used.

Chromatography, Gas↗
PubMed1981

Use of maximal expiratory flow-volume curves with air and helium-oxygen in the detection of ventilatory abnormalities in population surveys.

Flow-volume curves with air and helium, and spirometry were obtained in 423 subjects during epidemiologic health surveys; subjects were divided into 4 groups: nonsmokers and smokers not exposed to air pollutants at work, and nonsmoking and smoking grain elevator workers. The data obtained from 78 healthy nonsmokers who were not exposed to any air contaminants at work and had no respiratory symptoms were used to develop "normal" prediction equations for each of the following parameters: forced expiratory volume in one second (FEV1), maximal mid-expiratory flow, maximal expiratory flow at 50% of vital capacity while breathing air (Vmax50), the increase in Vmax50 after breathing a mixture of helium and O2 (delta Vmax50), and the volume of isoflow (VisoV). The prediction equations thus obtained from normal nonsmokers agreed with those published in the literature. The coefficient of variation was higher for delta Vmax50 (40.7%) and VisoV (57.6%) than for FEV1 (17.7%) or Vmax50 (27.7%). Comparison of results in smokers and nonsmokers who were not exposed to any air contaminants at work indicated that Vmax50 was the best test for discriminating the effect of cigarette smoking, whereas delta Vmax50 and VisoV were not significantly different. The FEV1 was the best discriminator of the effects of grain dust. There was poor concordance among FEV1, Vmax50, and delta Vmax50 or VisoV. We concluded that FEV1 and Vmax50 are more useful parameters than are delta Vmax50 and VisoV for detecting ventilatory abnormalities in a smoking, working population and in grain elevator workers. The results suggest that the addition of the more time-consuming test, the helium flow-volume curve, is unlikely to contribute any further useful information among the populations surveyed.

Air Pollutants, Occupational↗
PubMed1981

Salmonella infections in Singapore.

The incidence of typhoid and paratyphoid in Singapore from 1976 to 1979 is reviewed. Common Vi-phage types were A, B1, B2, D1, D2 and E1. Most of the paratyphoid cases were imported but an outbreak of paratyphoid A started in 1979 for the first time in Singapore with a predominance of untypable phage type strains. Most of the strains of Salmonella typi and Salmonella paratyphi A & B were susceptible to antibiotics, except for 4 strains of S typhi isolated from imported cases. Infections caused by Salmonella typhimurium were most common in children under five. The strains were initially multiple-resistant to antibiotics, but gradually became more susceptible with decline in the number of cases. Among the salmonella serotypes isolated from clinical materials, Salmonella oranienburg showed multiple-resistance to antibiotics and started an outbreak among children in October 1978. A total of 55 serotypes other than salmonella typhimurium was isolated between 1976 and 1979, with most of them susceptible to the antibiotics except triple-sulpha.

Child, Preschool↗
PubMed1981

Vibrio infections in Singapore.

Both symptomatic and asymptomatic Vibrio infections, caused by V cholerae, V parahaemolyticus and NAG vibrios, occurred in Singapore. V cholerae are introduced into the country from time to time, but the risk of transmission of infection in the community is negligible in the presence of a high standard of environmental sanitation and a well-established system of epidemiological surveillance. As cholera is probably transmitted through contaminated food, shellfish imported from cholera-endemic countries are regularly monitored for the presence of V cholerae. Vigilance has also been stepped up in the laboratory in view of the possibility of introduction of multiple-antibiotic resistant V cholerae strains into the country. V parahaemolyticus is one of the commonest causes of bacterial food poisoning in Singapore because of the preference of the local population to consume raw or partially cooked seafood. 78% of a variety of imported seafood were found to be contaminated with V parahaemolyticus. Infections caused by NAG vibrios are infrequent, and the mode of transmission has not been established.

Adolescent↗
PubMed1980

Urease-positive Vibrio parahaemolyticus strain.

An unusual strain of Vibrio parahaemolyticus was isolated from the site of a perforated appendix. This was the first reported case in which the vibrios demonstrated a positive urease reaction. In other respects, the strain conformed to the general characteristics of V. parahaemolyticus. It was susceptible to chloramphenicol, sulfamethoxazole-trimethoprim, tetracycline, neomycin, triple sulpha, gentamicin, and polymyxin B and produced the "Kanagawa phenomenon". However, its role as a causative pathogen of the diarrhea of the patient was debatable.

Acute Disease↗