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Biomedical subjects

R Wong

Publications and source records attributed to R Wong.

At least 181 records · Page 10Linked to original sources
PubMed1988

Reoperation within 2 years of aortofemoral bypass.

The authors analysed 267 consecutive primary aortofemoral grafts to identify the reasons for reoperation within the first 2 years postoperatively. Forty-one (8%) of the 521 limbs required a second operation. Precursors to reoperation were: occlusion of a superficial femoral artery (12%), gangrene (27%) and severe acute ischemia (35%). The rationale for reoperation was classified as technical 11, questionable selection (candidates for percutaneous transluminal angioplasty or inappropriate operation) 9, disease progress 11, residual symptoms 9, contralateral symptoms 1. The commonest technical problem was blind endarterectomy which preceded seven reoperations, five for thrombosis of the graft or a superficial femoral artery which was patent initially. Although 218 limbs had an occluded or severely stenosed superficial femoral artery, only 26 (12%) required reoperation within the first 2 years. The authors believe that the incidence of reoperation after aortofemoral bypass can be reduced by identifying the limbs at risk, by appropriate selection for percutaneous transluminal angioplasty, avoiding blind outflow endarterectomy and considering concomitant femoropopliteal bypass when gangrene is present.

Adult↗
PubMed1987

Adaptations of neurotransmitter synthesis to chronic hypoxia in cell culture.

Tyrosine hydroxylase and tryptophan hydroxylase are widely held to be rate-limiting for the synthesis of the catecholamines and serotonin, respectively. Both enzymes are oxygen-requiring and kinetic properties suggest that oxygen availability may limit synthesis of these neurotransmitters in the brain. Using pheochromocytoma cells as a cell culture model for catecholamine synthesis, and neuroblastoma cells as a model for serotonin synthesis, enzyme activity was measured under control and hypoxic conditions. Both tyrosine hydroxylase and tryptophan hydroxylase activity increased substantially with chronic exposure but not with acute exposure. In the case of tyrosine hydroxylase, increased enzyme content with hypoxia accounts for increased activity. This suggests a mechanism for the maintenance of neurotransmitter synthesis with chronic hypoxia. Measurement of intracellular metabolites revealed no change in dopamine or norepinephrine in hypoxic pheochromocytoma cells, consistent with a simple adaptive mechanism. However, in neuroblastoma cells, hypoxia was associated with an increase in serotonin concentration. The reasons for this are still unclear.

Animals↗
PubMed1987

Lack of response to suramin in patients with AIDS and AIDS-related complex.

Forty-one homosexual men with the acquired immune deficiency syndrome (AIDS) or AIDS-related complex were treated with 0.5, 1.0, or 1.5 g of suramin weekly for up to six months. In no patient was evidence of symptomatic improvement or regression of Kaposi's sarcoma shown. Opportunistic infections developed in 16 patients during therapy. Only six patients (15 percent) became human immunodeficiency virus (HIV) culture-negative during treatment, despite documentation of adequate serum suramin levels. All but one of these six have had disease progression. Decreases in the numbers of total T4 cells with time were observed in both AIDS and AIDS-related complex subgroups. Toxicity was significant and consisted of fatigue, fever, and hepatic and renal dysfunction, all of which were observed most frequently with the 1.0 or 1.5 g dosages. Fatal hepatic failure developed in two patients, and adrenal insufficiency was documented in eight patients. Suramin is a toxic agent that shows no virologic, immunologic, or clinical benefit in patients with HIV-related disease.

AIDS-Related Complex↗
PubMed1987

Evidence for peripheral blood B lymphocyte but not T lymphocyte involvement in multiple myeloma.

Because there is controversy regarding whether subsets of peripheral blood lymphocytes (PBLs) are part of the malignant clone in patients with multiple myeloma, we studied this question by immunoglobulin and T cell receptor gene analysis. Southern blot analysis with antibody probes demonstrated clonal immunoglobulin gene rearrangements in PBLs of seven of nine patients that were identical to those seen in their marrow plasma cells. Circulating plasma cells were not detected in any of these patients. In contrast, no patient demonstrated clonally rearranged T cell receptor genes. In one sequentially studied patient, PBLs obtained at diagnosis when he had stage I (Durie-Salmon) contained only germline DNA, while analysis of PBLs at relapse (stage III) revealed a clonally rearranged band. These data confirm the notion that circulating lymphocytes in patients with myeloma are part of the malignant clone and, furthermore, these malignant cells are of B cell rather than T cell lineage.

Aged↗
PubMed1986

Adrenocortical responsiveness to novelty in the hamster.

The adrenocortical response to increasing periods of exposure to a novel cage, as well as the effects of returning hamsters to their familiar home cages, were examined. We found that a five min exposure to a novel cage was insufficient to activate the pituitary-adrenal system, but that cortisol levels increased significantly as duration of exposure increased from 15 to 30 min. In contrast, returning hamsters to their home cages for at least 15 min following the 15 min novel cage exposure produced a significant drop in plasma levels of cortisol. Finally we found that males exhibit a greater cortisol response to novelty than females, indicating a sexual dimorphism which is the reverse of that reported in other rodents.

Adrenal Cortex↗
PubMed1986

Caloric balancing and sucrose intake of hamsters and gerbils.

In Experiment 1, hamsters and gerbils were randomly assigned to groups that were given a choice between pairs of sucrose solutions differing in concentration. The groups consisted of a control along with the following pairs: 2% and 6%; 2% and 8%; 2% and 12%; 2% and 18%; 6% and 8%; 6% and 12%; 6% and 18%; 12% and 18%. They were tested for 15 days, and the results indicated that the animals drank more from the cylinder containing the higher concentration. The principle of "least consummatory effort" appeared to be substantiated by these results. In Experiment 2, other hamsters and gerbils were randomly assigned to one of six groups receiving either 0.5%, 2%, 6%, 10%, 14%, or 18% sucrose solution. Analysis of their intake of sucrose and Purina Lab Chow indicated that their total caloric intake was relatively constant, reflecting the fact that an increase of consumption of the solutes in the sucrose solution reduced their intake of the stock diet. The results from both experiments indicated that although the caloric intake of hamsters relative to body weight was greater than that of gerbils, the proportion of total calories taken from sucrose was greater for the latter than for the former.

Animals↗
PubMed1985

Prospective study of side effects associated with the use of silver sulfadiazine in severely burned patients.

We report the results of a prospective study of 45 burn patients in whom serum and urine levels of cream constituents (sulfadiazine and propylene glycol) were determined and correlated with clinical parameters and the presence of an immune response to sulfadiazine. Propylene glycol, measured by gas chromatography, was found in the serum of 53% of study patients. Sulfa, determined by spectroscopy, was found in the serum of all patients, with values as high as 9.1 mg/dl within 24 hours of topical application. Ninety percent of tested patients had circulating sulfadiazine antibodies, predominantly IgG. Fourteen patients died, 11 of whom had interpretable renal biopsies. Five of these biopsies showed positive immunofluorescent linear or granular staining for IgG, IgM, IgA, or C'3; none of these 5 patients had clinical evidence for the nephrotic syndrome. The association between antisulfadiazine antibodies, circulating immune complexes, immunoglobulin disposition on glomerular basement membranes, and topical application of silver sulfadiazine provides evidence for sulfadiazine sensitization in patients with severe burns.

Administration, Topical↗
PubMed1984

Multiple aortic root echoes: clinical, radiographic, and angiographic correlations.

Multiple diastolic echoes in the aortic root on M-mode echocardiography may represent fibrosis or calcification of the aortic wall, aortic leaflets, or proximal portions of the coronary arteries. In this study, 83 patients with multiple diastolic echoes were evaluated by cardiac fluoroscopy and the incidence of valvular, coronary, and aortic wall calcification was determined. In patients with multiple diastolic echoes who have no evidence of significant aortic stenosis (aortic valve opening less than or equal to 1.0 cm) or aortic insufficiency (fine fluttering of the anterior leaflet of the mitral valve), the presence of multiple diastolic echoes was highly associated with significant coronary artery calcification (64%) with over two-thirds having multivessel involvement. Patients referred for echocardiography who are free of significant aortic stenosis or aortic insufficiency by echocardiographic criteria who are found to have multiple diastolic echoes in the aortic root should be evaluated further for the possible presence of significant multivessel coronary artery disease.

Adult↗
PubMed1984

Feeding inhibition produced by concurrent sucrose ingestion in gerbils and hamsters.

The daily 1-h intake of solid diet, 7% sucrose solution, and water of gerbils and hamsters tested for a 15-day period was investigated. Results of Experiment 1 indicated that gerbils provided with sucrose solution in addition to Purina rat chow showed an inhibition of food intake relative to control gerbils not given access to sucrose solution. However, experimental animals did not differ from control animals in either body weight loss or total caloric intake. For Experiment 2, results indicated that hamsters provided with sucrose solution in addition to sunflower seeds did not differ in their daily 1-h intake of seeds from control hamsters that had access to sunflower seeds. In Experiment 3, gerbils were tested under the same conditions as those of Experiment 2, and results indicated that concurrent sucrose ingestion inhibited the intake of sunflower seeds. The implications of these species differences in reactions to the test conditions are discussed.

Animals↗
PubMed1983

Consummatory behavior and adrenocortical responsiveness in the hamster.

In this study we examined the effects of consummatory behavior on adrenocortical activity in the golden hamster (Mesocricetus auratus). We found that: (1) Animals tested in their home cage began drinking faster and drank more water than animals tested in a novel cage. (2) Basal levels of cortisol were not elevated following 24 hr water deprivation. (3) Placement in a novel cage produced significant cortisol elevations. However, if water was available, cortisol levels were reduced and did not differ significantly from presession (basal) levels. (4) Opportunity to drink while in the home cage produced no significant change in cortisol. All animals were water-deprived for 24 hr prior to testing and no sex differences were observed on any of these measures. In a second experiment we examined adrenocortical inhibition in water-deprived animals tested in a novel cage which was Empty or which allowed access to Food, Water or Sanicel bedding. Presence of food did not reduce cortisol levels; however, presence of either water or Sanicel reduced plasma corticoids to basal levels.

Adrenal Cortex↗
PubMed1983

Artifacts produced by moving grids.

Anti-scatter grids reduce the amount of secondary radiation contributing to the image and improve the signal-to-noise ratio. However, they may also lead to the creation of linear artifacts representing the shadows of the radiopaque septa. Grid motion perpendicular to the septa during the exposure can cause blurring of the artifacts; however, the wider septa of recently proposed grids increase the difficulty of suppressing the artifacts entirely. Physical characteristics which affect perceptibility of grid-line artifacts and the conditions needed for their elimination are analyzed. Sufficient grid movement can eliminate overlap artifacts, while synchronization of linear grid motion with exposure time can suppress artifacts for relatively small grid movements.

Technology, Radiologic↗
PubMed1983

Epidemiologic health study of workers in an aluminum smelter in British Columbia. Effects on the respiratory system.

A health survey was carried out on all white males in an aluminum smelter in British Columbia. The survey consisted of a medical-occupational questionnaire, spirometry, chest radiography, and environmental monitoring. We have compared the results of a respiratory survey in 713 workers in the office and casting department with no significant exposure to air contaminants (control workers) with those of 797 potroom workers: 495 who spent more than 50% of their working time in the potroom (high exposure) and 302 workers who spent less than 50% of their working time in the potroom (medium exposure). Potroom workers (high) had a significantly greater prevalence of cough and wheeze than did those in the control group, and they had significantly lower mean forced expiratory volume in one second and maximal midexpiratory flow rate than did those in the control group after adjustment had been made for differences in age, height, and smoking habits. Potroom workers (medium) had a slightly greater prevalence of respiratory symptoms and lower lung function than did workers in the control group, but the differences were not significant. We were unable to demonstrate potroom asthma. The levels of total fluoride, gaseous fluoride, particulate fluoride, sulphur dioxide, and total particulates found in the potroom at the time of the study were below the currently accepted threshold limit values, but the levels of benzo-alpha-pyrene were high.

Adult↗
PubMed1983

Reduction of fluoroscopic exposure for the air-contrast barium enema.

In a fluoroscopic imaging system, image quality and patient dose are both affected by the optical system linking the image intensifier with the video camera. The effect on patient exposure of increasing the optical iris aperture size over that required for other procedures performed on the same imaging system was investigated for the air-contrast barium enema examination. Using a large-area transmission ionisation chamber to monitor the Roentgen-area-product of entrance exposure, a decrease in fluoroscopic radiation of greater than 50% was clinically documented for a fluoroscopic system utilising kVp and mA variable automatic brightness control. For this iris change, the video image was of acceptable quality for positioning and monitoring the patient, and no deleterious effect was detected in the conduct of the air-contrast exam. The availability of a variable-sized operator-selectable iris diaphragm would permit this dose-reduction approach to be extended to other fluoroscopic procedures.

Air↗