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Biomedical subjects

D Wong

Publications and source records attributed to D Wong.

At least 217 records · Page 12Linked to original sources
PubMed1991

Pseudophakic retinal detachment.

A total of 93 cases of pseudophakic retinal detachment are reported. The present study showed that vitreous loss had occurred during cataract surgery in 28% of eyes, indicating that anterior segment complications are an important contributory factor to aphakic retinal detachment in these cases. There was impairment of the retinal view in 46% of eyes, and in 22.5% no retinal breaks could be identified. The main factor responsible for poor visibility was inadequate pupillary dilatation, which was found particularly in association with the use of iris-supported lenses. Detachment of the macula was unexpectedly found to occur in as many as 88% of cases. Reattachment of the retina either by conventional detachment procedures or by pars plana vitrectomy was achieved in 76.3% of eyes. Complications directly attributable to the presence of an intraocular lens (such as dislocation or haemorrhage) are described. Failure of surgery was more likely to occur in eyes exhibiting a poor fundal view, in which the detection of retinal breaks was difficult. The best results were achieved in eyes in which posterior-chamber lenses had been implanted.

Adult↗
PubMed1991

Comparison of cardiovascular effects of pipecuronium versus vecuronium in patients receiving sufentanil anesthesia for myocardial revascularization.

This study was designed to compare the cardiovascular effects of pipecuronium bromide (PIP) to vecuronium (V) when combined with sufentanil (SF) in patients undergoing coronary artery bypass surgery. Eighty-two patients were studied; 40 were normotensive and 42 had hypertension currently controlled by pharmacological therapy. All patients were randomly assigned to receive either intravenous V, 0.12 mg/kg, or PIP, 0.10 mg/kg. Anesthesia was induced with SF, 6 micrograms/kg, while breathing 100% oxygen. Hemodynamic data including heart rate, mean arterial pressure, pulmonary capillary wedge pressure, central venous pressure, cardiac index, systemic vascular resistance, pulmonary vascular resistance, and left ventricular stroke work index were collected at five points: prior to induction, 3 and 6 minutes after the complete administration of PIP or V, and 3 and 6 minutes after intubation. There were no statistical differences in hemodynamic changes associated with either PIP or V. In addition, there were no statistical differences in the hemodynamic parameters measured at the five time points between the normotensive and hypertensive patient groups. This study demonstrates that there are no significant hemodynamic changes between SF/PIP and SF/V when used during coronary artery surgery. Due to its associated stable hemodynamics, as well as its long duration of action, PIP could become a commonly used muscle relaxant for anesthesia for cardiac surgery.

Androstane-3,17-diol↗
PubMed1991

Auer rod-like inclusions in circulating lymphoma cells.

Circulating malignant lymphocytes from a 55-year-old woman with small cleaved follicular center cell lymphoma contained azurophilic splinter-shaped cytoplasmic inclusions. By light microscopic and ultrastructural criteria, these structures closely resembled Auer rods found in acute myeloid leukemia; however, the authors could not find cytochemical evidence of lysosomal origin (results were negative for myeloperoxidase, Sudan black B, acid phosphatase, and periodic acid-Schiff). Immunostaining and flow cytometric analysis confirmed a monoclonal IgM-kappa immunophenotype of the circulating malignant lymphoid cells. The inclusions did not show specific immunoglobulin staining by light microscopic or electron microscopic immunostaining techniques. The authors conclude that these membrane-bound inclusions probably represent aberrant lysosomes in the malignant cells.

Female↗
PubMed1991

Personality. Type A behavior, and the effects of beta-blockade.

In a previous report, it was shown that a dimension of personality entitled dependence/independence could be used to distinguish the cardiovascular and catecholaminergic response to stress in type A individuals. This study is a continuation of the previous work. It examines the relative effects of beta-blockade on stress-induced changes in heart rate, blood pressure, and catecholamines in two groups of type A individuals who differ in reactivity. Sixty-six healthy, middle-aged men with type A behavior were classified as dependent (high reactivity) or independent (low reactivity). The effects of beta-blockade on the two groups were tested in a randomized, double-blind, crossover trial utilizing a mental stressor, a physical stressor, and work day monitoring. Results showed that, in comparison with the independent type As, those who had been classified as dependent had higher heart rates in all three stress conditions and had higher epinephrine levels during both the mental and physical stressors. For both groups, beta-blockade lowered the heart rate and systolic blood pressure but increased norepinephrine with the mental stressor and epinephrine and norepinephrine with the physical stressor. It also reduced the mean work day heart rate. For the dependent type As, the drug had a greater effect on increasing epinephrine during the physical stressor and by reducing the percent of the work day spent in high heart rate zones. The results are discussed from the point of view of identifying type As who may be particularly coronary prone and the potential effects of beta-blockade on the reactivity associated with type A behavior.

Adult↗
PubMed1991

Observation of perturbations in a lumped-element model of the vocal folds with application to some pathological cases.

In this paper a mass-spring model is developed that is a hybrid of the two-mass and the longitudinal string models, proposed by Ishizaka and Flanagan [Bell Sys. Tech. J. 51, 1233-1268 (1972)] and Titze [Phonetica 28, 129-170 (1973)], respectively. The model is used to simulate the vibratory motion of both the normal and asymmetric vocal folds. Mouth-output pressure, lateral tissue displacement, phase plots, and energy diagrams are presented to demonstrate the interaction between vocal fold tissue and the aerodynamic flow between the folds. The results of the study suggest that this interaction is necessary for sustained large amplitude oscillation because the flow supplies the energy lost by the tissue damping. Tissue mass and stiffness were varied locally or uniformly. Decreased stress in the longitudinal string tension produced subharmonic and chaotic vibrations in the displacement, velocity and acceleration phase diagrams. Similar vibratory characteristics also appeared in pathological speech data analyzed using time domain jitter and shimmer measures and a harmonics-to-noise ratio metric. The subharmonics create an effect that has been perceptually described as diplophonia.

Computer Simulation↗
PubMed1991

Clinical utility and specificity of anticardiolipin antibodies.

Established solid phase assays for anticardiolipin antibodies (aCL) are often characterized by high levels of nonspecific binding. As a result, only very high levels of aCL have been reported to be associated with a variety of clinical conditions including systemic lupus erythematosus (SLE), recurrent intravascular thrombosis and unexplained recurrent fetal loss. We have developed an ELISA replacing direct evaporation of soluble cardiolipin with cardiolipin micelles in physiological saline as the antigen binding step in the assay. Levels of IgG aCL were detected in various sera at dilutions of 1/100 to 1/3200, showing improved assay sensitivity. Assay specificity was determined using double stranded DNA and ovalbumin as irrelevant binding antigens and no crossreactivity was found. The controversial use of Tween 20 in the assay was investigated and results showed it decreases nonspecific binding without interfering in antibody detection. This assay has enabled us to identify differences in the prevalence and level of aCL antibodies in sera from healthy nonpregnant controls (0/25 positive), healthy pregnant controls (5/47 positive for IgG and 8/47 positive for IgM) and from women with unexplained recurrent fetal loss (16/62 and 14/62 positive, respectively). We support the observation that aCL are not normally distributed, and therefore nonparametric methods of statistical analysis are necessary to determine population prevalence. We confirm that aCL IgM are a relatively nonspecific finding, and extreme caution must be used in basing any clinical decisions on the presence of this antibody alone.

Adolescent↗
PubMed1990

Prevalence of human parvovirus (B19) and rubella virus infections in urban and remote rural areas in northern Brazil.

Sera from inhabitants of Belém, Pará (542 sera), Brazil and of members of 3 Brazilian tribes--Tiriyo/Alto Paru (near Surinam) (212 sera), Xicrin (128 sera), and Mekranoiti (121 sera)--of different age and sex groups were tested for the presence of specific antibody against human parvovirus (B19) (RIA) and rubella virus (latex agglutination test). Parvovirus (B19) IgG was found in 42.6% of the population sample from Belém but in only 4.7 to 10.7% of the members of the tribes. Rubella virus antibody was found in 72.7% of the sera from Belém but approaching a prevalence of 85-90% in age groups above 20 years. In the tribes rubella virus antibody was detected in 36.9 to 72.6% of all sera. There were remarkable sex differences of antibody prevalence in several age groups of the population from Belém and of the tribal populations. About a quarter of the skin rashes in Belém that were not attributable to infections with rubella, measles, or arboviruses were caused by recent B19 infections.

Adolescent↗
PubMed1990

Heart valve operations in patients with active infective endocarditis.

Sixty-two consecutive patients underwent heart valve operation for active infective endocarditis. There were 42 men and 20 women whose mean age was 49 years (range, 21 to 79 years). The infection was in the aortic valve in 37 patients, the mitral valve in 18, the aortic and mitral valves in 5, and the tricuspid valve in 2. Twenty-four patients had prosthetic valve endocarditis. Staphylococcus and Streptococcus were responsible for 86% of the infections. Annular abscess was encountered in 33 patients. Complex valve procedures involving reconstruction of the left ventricular inflow or outflow tract or both were performed in 31 patients. There were three operative deaths (4.8%). Predictors of operative mortality were prosthetic valve endocarditis, preoperative shock, and annular abscess. Patients were followed for 1 month to 130 months (mean follow-up, 43 months). Only 1 patient required reoperation for persistent infection. There were ten late deaths. Most survivors (96%) are currently in New York Heart Association class I or II. The 5-year actuarial survival was 79% +/- 7%. These data demonstrate excellent results in patients with native valve endocarditis, and support the premise that patients with prosthetic valve endocarditis should have early surgical intervention.

Adult↗
PubMed1990

Risk factors for squamous cell carcinoma of the skin in Saskatchewan, Canada.

Completed questionnaires regarding suspected risk factors for skin cancer were completed by 178 cases of SCC of the skin in Saskatchewan, Canada, and 284 age- sex- and location-matched controls. Significant risk factors identified using chi2 analyses were: farming, family history of skin cancer, light eye color, blond or red hair color, skin types I or II, obvious freckles in childhood, history of severe sunburn, and the use of the herbicide 2,4-Dichlorophenoxy acetic acid. The following relative risks were identified: (1) All cases of SCC of the skin and matched controls: agricultural occupation 1.49, history of severe sunburn 1.49. (2) All men with SCC of the skin and matched controls: history of severe sunburn 1.36 (3) All women with SCC of the skin and matched controls: agricultural occupation 1.83, and skin types I or II 1.48. No association was noted on our study between a history of psoriasis and development of SCC. Neither was an association between smoking and SCC found.

Carcinoma, Squamous Cell↗
PubMed1990

Dibutyryl cyclic AMP induces vimentin and GFAP expression in cultured medulloblastoma cells.

Evidence for the astrocytic lineage in medulloblastomas rests largely on the detection of the glial fibrillary acidic protein (GFAP) from which intermediate filaments (IF) specific for astrocytes are assembled. Astrocyte progenitor cells from the mouse neopallium however express another IF protein, vimentin, before they acquire GFAP in vivo and in vitro. The purpose of the current study was to determine if cells obtained from a focally GFAP-positive posterior fossa medulloblastoma previously shown to acquire GFAP in response to dibutyryl cyclic AMP (dBcAMP), also express vimentin before expressing GFAP. More than 80% of cells in the tumor section contained vimentin while fewer than 1% of cells contained GFAP; occasional clusters of malignant GFAP-positive cells and clusters of cells negative for both vimentin and GFAP were also identified in the tumor. One hundred per cent of cultured cells in the first 10 passages from the tumor contained vimentin and no cells expressed GFAP. When cells were cultured in the presence of dBcAMP. Western immunoblotting showed an increase in vimentin which reached maximal values within 24 h followed by an increase in GFAP which reached maximal values at 72 h. The increase in vimentin followed by that of GFAP in cultured medulloblastoma cells has not previously been reported and suggests that most astrocyte progenitors which are derived from medulloblastoma and cultured in vitro may be at a developmental stage which corresponds to the proastroblast stage in the developing mouse brain.(ABSTRACT TRUNCATED AT 250 WORDS)

Bucladesine↗
PubMed1990

Results and complications of conventional repair of bullous retinal detachment using posterior segment air injection.

The aims of this retrospective study were to determine the outcome of retinal detachment repair using the drainage, air injection, cryotherapy and explant surgical sequence ('D-ACE' technique) for bullous retinal detachments and also to identify the complications attributable to the injection of the gas. The D-ACE technique was used to repair 206 detachments over a ten year period of which 138 (67%) were successfully re-attached with a single operation. The sub-group of these patients (n = 66) with bullous retinal detachments who would be considered suitable for repair using the technique of pneumoretinopexy (PR) showed a single operation success rate of 85% after D-ACE. Complications attributable to the gas injection occurred in 18 eyes (8.5%). In only four of these (1.9%) did retinal surgery ultimately fail as a result of complications caused by injection of the gas, which represents 10% of all the failures. The results of this series show that the serious complication rate from injecting air into the vitreous cavity is low and that the success rate for treating relatively uncomplicated bullous retinal detachments using the D-ACE technique compares favourably with the results of other published series using either the D-ACE procedure or pneumoretinopexy.

Air↗
PubMed1990

Refractive changes in silicone filled eyes.

In this study we examined refractive changes of 34 eyes in 34 patients treated with silicone oil injection. Six patients presented with aphakic retinal detachment, another 14 were rendered aphakic after silicone oil injection, one was pseudophakic and 13 were still phakic at the time of writing this report. Silicone oil in the vitreous cavity induced a myopic shift in aphakic eyes and a hypermetropic shift in phakic eyes. This tended to render phakic high myopes and aphakes closer to emmetropia. The resultant refraction was dependent on the shape of the silicone oil bubble inside the eye and influenced by the posture of the patient. In phakic patients the ability to accommodate was markedly reduced.

Accommodation, Ocular↗
PubMed1990

Subretinal gas.

Two cases of subretinal gas are described. The circumstances in which this complication arose are important in understanding the mechanism by which gas gains access into the subretinal space. Evacuation of subretinal gas by posturing should be avoided as this leads to an increase in the extent of the retinal detachment and its extension anterior to involve the nonpigment epithelium of the pars plana. A technique for removing subretinal bubbles of expanding gases using vitrectomy and fluid/gas exchange is recommended.

Adult↗
PubMed1990

Type A behavior, personality, and sympathetic response.

This study examined, under two types of stress and during a typical workday, the moderating effects of the personality trait dependence/independence on the hemodynamic and catecholaminergic response in Type A individuals. During the mental stressor, Type As with strong dependency needs showed elevated heart rates and higher levels of epinephrine. During the physical stressor, they showed elevated heart rates and higher levels of norepinephrine. During the typical workday, both urinary catecholamines and mean daily heart rates were higher. It is suggested that these findings, which indicate greater sympathetic-adrenal response, are the result of a basic personality/behavior inconsistency and that Type A behavior may have an accentuated relationship to coronary disease when overlaid on a personality for which it is inconsistent.

Adult↗
PubMed1990

Developmental expression of proteolipid protein and DM20 mRNAs and proteins in the rat brain.

Proteolipid protein (PLP) and DM20, two abundant proteins of myelin, are produced from alternatively spliced mRNAs from the primary PLP gene transcript. Recent studies on the mouse, bovine and human central nervous systems have found that DM20 protein is expressed prior to PLP during development. As development proceeds, however, PLP becomes the predominant protein. This implies that there must be some form of regulation controlling the ratio of these proteins during development. If this regulation occurs during transcription or splicing, the PLP/DM20 mRNA ratio should mimic the PLP/DM20 protein ratio during development. In order to study these closely related mRNAs, we developed a method that used oligonucleotide probes to specifically identify PLP or DM20 mRNA. In this study, we established that (1) as with other species studied, the DM20 protein is present at higher or equivalent levels to PLP during early rat brain development, and (2) PLP and DM20 mRNAs have essentially identical developmental profiles in the rat, although the DM20 mRNA is expressed at lower levels than PLP mRNA. Since the PLP/DM20 protein ratio in young rats does not reflect the PLP/DM20 mRNA ratio, the mechanism of regulation responsible for altering the PLP/DM20 protein ratio during development must occur after transcription and splicing. Possible posttranscriptional mechanisms controlling the ratio of these proteins during development are discussed.

Animals↗
PubMed1990

Tolerance to beta 2-agonists in patients with chronic obstructive pulmonary disease.

Eleven patients with severe COPD were examined to determine whether tolerance to beta 2-agonists developed after long-term inhalation therapy with these agents. Before the study all patients were on regular treatment with inhaled salbutamol for six months. At the beginning of the study, response of FEV1 to inhaled salbutamol was measured. Dose-response curves were measured after three weeks of treatment with ipratropium bromide and again after a three-week course of inhaled salbutamol. After ipratropium bromide treatment, responses to low doses of salbutamol tended to be larger than after salbutamol treatment, but differences were not significant. Three hours after the last inhalation of salbutamol the FEV1 was lower on days 1 and 42 than on day 21. We conclude that long-term inhalation therapy with beta 2-agonists in patients with COPD decreases the duration of the bronchodilation produced by the same agents but does not affect the peak response.

Administration, Inhalation↗
PubMed1990

Metabolic activation of nitropyrenes and diesel particulate extracts.

The aim of this research was to investigate the possible risks of genotoxicity associated with human exposure to diesel engine emissions. We sought to identify and evaluate the critical components of such emissions by using a variety of short-term biological systems. Adducts formed between benzo[a]pyrene and DNA in several short-term test systems have been thoroughly investigated. Although benzo[a]pyrene has long been used as an index of the potential carcinogenicity of polycyclic aromatic hydrocarbon mixtures and is present in diesel engine emissions, it may not be the best measure of the carcinogenicity of these emissions if, indeed, they are confirmed to exert such an effect in humans. Certain nitroarenes, known to be present in diesel particulate extracts, are very potent mutagens in the Ames assay. The major adducts formed in Salmonella typhimurium with 1-nitropyrene (Howard and Beland 1982) and 1,8-dinitropyrene (Andrews et al. 1986; Fifer et al. 1986) have been identified. We undertook, therefore, a comparison of the DNA adducts formed between 1-nitropyrene, 1,3-dinitropyrene, 1,6-dinitropyrene, and 1,8-dinitropyrene and cellular DNA in various systems, including human bronchial segments, in rabbit lung and trachea, and mouse embryo fibroblast C3H/10T1/2 cells, with those reported to be formed in S. typhimurium. In these studies, we administered radiolabeled nitropyrenes, analogous to the treatments previously employed for testing benzo[a]pyrene, and isolated and digested the modified DNA. We then compared elution times, by high-pressure liquid chromatography, of the radioactive adducts with synthetic standards. Not all combinations of exposures were undertaken, since the direction of the investigations changed to include studies on adducts formed in animals exposed to diesel engine emissions themselves. Of the samples studied, metabolism of 1-nitropyrene was most evident in the human bronchial tissue. Little metabolism was evident in duodenal and colonic samples. Mouse C3H/10T1/2 embryo fibroblasts showed no detectable metabolism of, DNA adduct formation with, or transformation by 1-nitropyrene. DNA adducts were detected in cells exposed to 1,8-dinitropyrene and traces of adducts were formed with either 1,3-dinitropyrene or 1,6-dinitropyrene. Measurements of DNA adducts formed after treatment with [4,5,9,10-3H]-1-nitropyrene in rabbit tracheal samples showed that only about 2 to 15 percent of the associated radiolabel could be accounted for as the previously identified C-8 adduct. To facilitate the quantification of adduct levels that might occur in humans and laboratory animals exposed to the nitroarenes in diesel engine emissions, antisera were prepared against DNA modified with 1-nitrosopyrene.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗