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Biomedical subjects

G Lawson

Publications and source records attributed to G Lawson.

At least 37 records · Page 2Linked to original sources
PubMed1999

Carbon dioxide laser debulking for obstructing endolaryngeal carcinoma: a 10-year experience.

The results of the carbon dioxide (CO2) laser debulking procedure for obstructing endolaryngeal carcinoma were analyzed in terms of efficiency, complications, secondary tracheotomy rate, and peristomal recurrence rate in a series of 50 patients consecutively managed at our department. The CO2 laser was used to reestablish a safe airway without resorting to tracheotomy and without performing a transoral resection. Our series included 42 patients in a pre-definitive treatment group (group 1) and 8 patients in a palliation group (group 2). Complications included death, pneumonia from inhalation, and cutaneous burns in 2 patients, 1 patient, and 1 patient, respectively. Thirty-two percent of patients required a repeat laser treatment to maintain the airway. Overall success rates of 92.8% and 87.5% were achieved in group 1 and group 2 patients, respectively. None of the variables under analysis could predict the success of the CO2 laser debulking procedure. The overall incidences for secondary tracheotomy were 4.7% and 0% in group 1 and group 2 patients, respectively. Peristomal recurrence was not encountered in patients managed with definitive therapy with curative intent.

Adult↗
PubMed1999

Correcting vocal fold immobility by autologous collagen injection for voice rehabilitation. A short-term study.

We report on a short-term clinical study of injectable autologous collagen (Vocalogen) used to correct dysphonias arising from vocal fold immobility. The collagen is extracted from skin taken from the lower abdominal quadrant area or from just above the bikini line. About 30 cm2 of skin are required to provide 2 mL of injectable collagen. The histologic examination of the preparation before injection disclosed the presence of elastin fibers and some clusters of epithelial cells, beside the collagen fibers. The collagen is naturally reticulated, and the molecule is preserved in its entirety. The technique is exactly the same as that reported for bovine collagen: injection into Reinke's space, under general anesthesia, monitored by direct microlaryngoscopy. The amount injected is also similar: 1.5 mL for correction of glottic insufficiency in which the immobile vocal fold is in the intermediate position. Eight patients were injected, and the average follow-up was 4.5 months. Voice assessments made before and after the treatment included stroboscopy, subjective and perceptual judgments, and aerodynamic and acoustic measurements. The functional results were similar to those obtained with bovine collagen. No complications arose. The probability of any hypersensitivity reaction, always a possibility to be feared with bovine collagen, is negligible with the autologous collagen. Long-term results are as yet unknown, but from the fact that the collagen molecular structure is intact and there is little risk of foreign body response, it would be expected that autologous preparations would be more stable than bovine collagen; this appears to be the case in cosmetic applications. Autologous collagen could be employed for the same indications as bovine collagen, provided that a delay of 45 days (the time required to prepare the injectable collagen) is acceptable. The amount of collagen required is also a limiting factor, since the patient's own skin is the starting donor material.

Aged↗
PubMed1999

Palliative treatment for tracheal stenoses using carbon dioxide laser and the Gianturco stent. Long-term results.

Between September 1992 and March 1998, the self-expandable Gianturco prosthesis was inserted in 23 patients suffering from tracheal stenosis. After radial incision and dilation of the stenosis as described by Shapshay, the positioning of the stent was performed during an endoscopic procedure under optical control. The prosthesis used was a double-ring stent 50 mm long and 20 mm in diameter. The follow-up period ranged between 0.5 and 67 months with an average of 31 +/- 18 months. Pulmonary function tests showed an average improvement of the peak expiratory flow (50%) from preoperative results of 1.06 +/- 0.60 L/s to short-term postoperative results of 2.08 +/- 0.78 L/s and long-term postoperative results of 2.11 +/- 0.78 L/s. The mean peak inspiratory flow (50%) improved from 1.43 +/- 0.85 L/s to 2.40 +/- 1.29 L/s at short term and to 2.56 +/- 1.20 L/s at long term. Eight patients out of the 23 had to undergo a second endoscopic procedure: 3 patients for granuloma vaporization; 1 patient to change a malpositioned stent; 2 patients to add a second stent because of insufficient tracheal enlargement; and 2 patients to resect mucosal membranes between the 2 stent rings and to place a second stent. Optical control of the accurate positioning and use of this model of Gianturco prosthesis helped to avoid the severe complications described in the literature (migration, extrusion, fracture, wall erosion. and hemorrhage). The follow-up must particularly target the prevention of granulomas. The self-expandable Gianturco prosthesis can be advocated for long-term palliative treatment of tracheal stenoses that are inoperable by an external surgical approach.

Aged↗
PubMed1999

Transoral laser microsurgery is the recommended treatment for early glottic cancers.

Medical terminology frequently mistakes the instrument for the surgical procedure: endoscopic excision of laryngeal cancers existed long before laser came into use. Lasing obeys the same rules as those of suspension laryngoscopy: if adequate laryngeal exposure is not attained, then the procedure is at risk of being incomplete and of providing few satisfactory results. Because a certain degree of literary anarchy exists in terms of definitions for the different cordectomy types, the Nomenclature Committee of the European Laryngological Society has proposed a classification. This categorization is a synthesis and a compromise between members of the Society who had developed and used, for several years, a personal classification. The proposed classification has two aims: to better understand each surgeon's technique in function of the tumoral extent; and to compare more rigorously the postoperative results. This classification includes the following procedures: Subepithelial cordectomy or decortication (Type I); Subligamentous cordectomy (Type II); Transmuscular cordectomy (Type III); Total or complete cordectomy (Type IV); Extended cordectomy encompassing the contralateral vocal fold (Type Va); encompassing the arytenoid (Type Vb); encompassing the ventricular fold (Type Vc); encompassing the subglottis (1 cm) (Type Vd).

Endoscopy↗
PubMed1998

Saturation of ecosystems with toxic metals in Sudbury basin, Ontario, Canada.

Mining and resource recovery activities have not been kind to ecosystems in the Sudbury basin, Ontario. The combination of logging, smelting, fires and erosion resulted in an unusual anthropogenic ecosystem of denuded barren land with lifeless lakes, or a micro-desert. Since the 1970s, however, the concerted efforts made to reduce the emissions and rehabilitate parts of the degraded ecosystem have resulted in improvements in water quality, and recoveries in phytoplankton, zooplankton, zoobenthos and fish communities but have had little impact on toxic metal concentrations in many lakes. We show that most of the catchments in the Sudbury basin have become saturated with Cu and Ni, and some with Zn and Pb. It is estimated that mobilization of metals stored in soils and glacial overburden by surface runoff, groundwater drainage and wind re-working of tailings can sustain the high concentrations of Cu and Ni in many lakes for well over 1000 years. Strategies to immobilize the pollutant metals in the watershed rather than further emission controls may be required for dealing with high levels of toxic metals in surface waters of the saturated ecosystems.

Copper↗
PubMed1998

A new epiglottoplasty procedure for the treatment of intractable aspiration.

Intractable aspiration may require diversion of the airway from the pharynx. The epiglottoplasty procedure involves suturing the epiglottis onto the perimeter of the larynx without creating resistance to the natural lines of force of the epiglottic cartilage. The procedure starts by an anterior subhyoid pharyngotomy. The epiglottis is released from the pre-epiglottic space and the thyroepiglottic ligament is sectioned. The disinsertion is completed in the laryngeal lumen by sectioning the epiglottis on each side by following its edges. The pharyngoepiglottic folds are preserved so as to serve as the rotational axis for the freed epiglottis. The petiole of the epiglottis is anchored to the posterior commissure and the free edge of the epiglottis above the ala and the angle of the thyroid cartilage, while the lateral sides of the suprahyoid epiglottis are sutured to the superior part of the arytenoids. This procedure was performed successfully in three patients with intractable aspiration.

Aged↗
PubMed1997

CO2 laser in the diagnosis and treatment of early cancer of the vocal fold.

A total of 74 patients underwent cordectomy using CO2 laser for either diagnosis or treatment of an early cancer of the vocal fold. Type I cordectomy consisted in the resection of the entire epithelium, while leaving the vocal ligament intact. Type II cordectomy involved removal of the vocal fold from the vocal process to the anterior commissure and passing through the inferior thyroarytenoid muscle. Type IIIA required vocal fold resection along the internal side of the thyroid ala, while type IIIB included removal of the anterior commissure. Type I cordectomies were carried out with an Acuspot micromanipulator, which provided a 250-micron-diameter beam for a working distance of 400 mm, and in the shot-by-shot cutting mode with 3 W power superpulse. This cordectomy was carried out in 39 patients and a dysplasia or an early carcinoma were detected in 45.9% of cases. Type II and type III procedures were performed with the Microslad micromanipulator having a 700-micron-diameter beam in the continuous cutting mode, 7 W power superpulse. Fifteen cases were treated by type II cordectomy, of which 3 T1aN0M0 cases underwent postoperative radiotherapy due to insufficient resections and 2 cases with T1bN0M0 tumors later underwent reconstructive laryngectomy. A type III cordectomy was used for 14 cases of T1aN0M0 carcinomas and 3 cases of severe dysplasia. The margins of resection were found to be positive histologically in 23.5% of these cases, making frozen section examinations mandatory at time of surgery. Results of all procedures showed that voice was best after a type I cordectomy where only the epithelium was resected. In the type II and type III cordectomies, the quality of voice depended on the development of a fibrous fold and the absence of anterior synechia in the healed larynx.

Adult↗
PubMed1997

Expression of E-cadherin adhesion molecule in vocal cord carcinomas.

E-cadherin is a 120 kDa transmembrane protein that plays a major role in the maintenance of cell-cell adhesion in epithelial tissues. In the present study its expression was examined immunohistochemically for the first time using paraffin-embedded archival tissues of 38 vocal cord carcinomas. Ten cases of vocal cord polyps were used as positive controls. According to our criteria, results showed that all but one of the polyps, in which staining was lost, had strong or moderate E-cadherin expression, whereas 32% of the cases with tumors showed preserved staining, and 68% of cases showed a reduced staining. E-cadherin expression was significantly correlated with histological stages, with a greater expression in carcinoma in situ and microinvasive carcinoma than in invasive carcinoma (P = 0.010). A significant correlation was also found between E-cadherin expression and the degree of tumor differentiation (P = 0.018). Some of these findings were consistent with previously published data using fresh tissues. Our study provides evidence that E-cadherin may be linked to progression and differentiation of laryngeal cancer and could play a role as a tumor-suppressor gene in this cancer.

Cadherins↗
PubMed1997

Castleman's disease in the neck: MRI.

We describe a case of Castleman's disease in a 8-year-old-boy who presented with a slowly growing mass in the upper neck. MRI showed a well-defined homogeneous mass with nonspecific signal features. Unusual features were a kidney-bean shape and the deep location in the suprahyoid region, the mass originating in the left retropharyngeal space.

Biopsy↗
PubMed1997

Evaluation of proliferating cell nuclear antigen (PCNA) in supraglottic carcinoma.

It is widely accepted that tumor invasion and metastasis are the primary causes for the lethal clinical outcome of cancers. In recent years, attention has been drawn to PCNA (Proliferating Cell Nuclear Antigen) to predict the prognosis of some cancers. In the present paper, we have studied anti-PCNA antibody PC10 in supraglottic cancer by means of immunohistochemistry using paraffin-embedded sections, to demonstrate its clinical significance in this type of malignancy. Twenty-two patients with supraglottic cancer, including T1 (5 cases), T2 (13 cases) and T4 (4 cases) with N- (14 cases) and N+ (8 cases), were investigated for the PCNA expression. The percentages of PCNA positive cells were divided into three groups: < 25%, 25-75%, > 75%, with the range from 10.6 to 95.2%. Results showed that PCNA was well correlated with lymph node metastasis, and appeared to have an inverse correlation with histopathological grades. In this small group, we did not find that PCNA was correlated with T stages and tumor size. However, compared with other T-stages and tumor sizes, the correlation between lymph node metastasis and PCNA seemed to have more clinical significance in T2-stage and in tumors larger than 2 cm. PCNA could be used as a marker in predicting the clinical outcome in supraglottic cancers. An analysis on a large scale is anticipated.

Adult↗
PubMed1996

Use of the CO2-laser micropoint micromanipulator for the treatment of laryngomalacia.

Between September 1989 and June 1994, 21 children (17 boys, 4 girls) with moderate to severe symptoms due to laryngomalacia underwent endoscopic surgery using the CO2-laser micropoint manipulator (shot-by-shot, 0.1 s, super-pulse, 2-3 W power; 280 microns beam; 400 mm working distance). Mean age of the children was 5 months (range, 1-11 months). The procedure was performed under high-frequency jet ventilation and consisted in the resection and/or vaporization of the aryepiglottic folds. This tissue removal could be extended to the laryngeal mucosa of the arytenoids and the lateral edge of the epiglottis. Results of surgery were excellent with normalization (8 patients) or, at worst, a very definite improvement of symptoms (4 patients). Furthermore, no complications occurred due to the technique used. These results have convinced us that the CO2-laser micropoint manipulator technique, with the "super-pulse" shooting mode and high-frequency jet ventilation, is by far superior to microsurgery with cold instruments when endoscopic treatment of laryngomalacia is indicated.

Endoscopy↗
PubMed1996

Contaminant migration from food packaging laminates used for heat and eat meals.

EU legislation requires that components from food contact plastics should not migrate significantly into the food. The nature and extent of species migrating from laminated materials used for packaging 'heat and eat' meals have been investigated. Selected target analytes included additives incorporated into the polyolefin, e.g. the Irganox and Irgafos antioxidants, the diisocyanate and polyol residues from the adhesive and oligomeric material from the nylon. The results identified a wide range of migrants arising from each of the individual components of the laminate. Some of the migrants have been identified as precursors of the principal components of the laminate as well as those anticipated from a knowledge of the laminate construction. The levels of migration for those components identified and quantified has been well below the legal limits. Some significant migrant species have been however left unidentified by this investigation.

Journal Article↗
PubMed1996

Thallium and cadmium in recent snow and firn layers in the Canadian Arctic by atomic fluorescence and absorption spectrometries.

Compared to the Antarctic and Greenland, the Canadian Arctic has seen extremely few trace metal studies on snow and ice. Surface, subsurface and depth samples of snow and firns were collected from the Agassiz Ice Cap, Ellesmere Island, Canada using clean room practices. Results for Tl (directly determined by LEAFS) and Cd (determined by GFAAS) are reported. To our knowledge, the thallium depth profile presented here is the first one so far reported for both polar systems, Greenland or other places. Tl concentrations peak in the winter-spring periods, when the Arctic atmosphere is loaded with foreign pollutants and suspended particulates which sometime severely reduce the visibility, creating a phenomenon commonly known as the Arctic haze. These results are in general accordance with the historical Arctic air pollution and acidity/conductivity data on ice cores. Surface concentrations of Tl range from 0.3 to 0.9 pg/g, which is a few times higher than those found in Antarctica. Cadmium shows seasonal characteristics similar to Tl although there is not a definite correlation between the two. However, there could be two predominant origins of metals which were deposited in the snow: Eurasian origin in January-April corresponding to high level metals (main deposition), and a less definite origin in May-December corresponding to low level metals.

Journal Article↗
PubMed1996

Internal and external environment of individuals with schizophrenia during alcohol and drug use.

Explanations for the high prevalence of alcohol and drug abuse in schizophrenia purport that substance use is related to social-affiliative needs or to symptom regulation. Neither explanation was adequate in describing substance-use episodes in the present longitudinal study. The study involved repeated interviews of 10 individuals with schizophrenia about their internal and external environment during substance use. Qualitative analyses of interview responses showed variability in multiple versus single episodes in a day and categories labeled Activities Prior to Use and Social Context of Use. Individual subject's responses each had a unique pattern that characterized their substance-use episodes.

Adult↗
PubMed1996

Posterior cordectomy and subtotal arytenoidectomy for the treatment of bilateral vocal fold immobility: functional results.

We report vocal and respiratory results following endoscopic CO2 laser therapy for bilateral vocal fold immobility in adduction. Two techniques were used: posterior cordectomy (PC) and subtotal arytenoidectomy (SA). Respiratory improvement was demonstrated by the peak expiratory flow/peak inspiratory flow ratio (PEF/PIF, normal = 1), which was less than 2 for 83% of patients following PC and for 81% following SA. As for vocal results, there were no significant quantitative differences between the two techniques. Mean maximum phonation time (/a/) was 6.8 +/- 2.6 s after SA and 7.8 +/- 1.6 s following PC. The phonation quotient was 288 +/- 116 ml/s after SA and 304 +/- 92 ml/s after PC. Mean vocal intensity was 62 +/- 4 dB after SA and 59 +/- 3 dB after PC. Vocal quality was measured by high-resolution vocal frequency analysis, as represented by a histogram. Peaks corresponding to fundamental frequency and first harmonics were preserved in more than 60% of patients in the two groups. Vocal preservation is better when the paralyzed folds are in the paramedian position, with the possibility of adduction (Gerhardt syndrome). SA is performed in our procedure, though it is longer and more difficult to perform than PC. PC often requires two procedures to achieve satisfactory results.

Adolescent↗
PubMed1996

Endoscopic treatment of tracheal stenosis using the carbon dioxide laser and the Gianturco stent: indications and results.

The self-expandable Gianturco stent was used in 11 patients with tracheal stenosis who where treated from September 1992 through July 1994. Under optical control, the stent was placed through a bronchoscope with an outside diameter of 9 mm after cross-section and dilation of the stenosis were performed with the carbon dioxide laser according to the Shapshay technique. The follow-up period varied from 3 to 22 months, with a mean of 12 +/- 6 months. Pulmonary function tests showed a mean improvement of the peak expiratory flow (50%), from 0.95+/-0.45 L/sec before the operation to 2.13+/-0.86 L/sec after the procedure. Radiologic and fibroscopic controls showed prosthesis stability. Three patients needed a second endoscopic procedure because of malposition of the stent, the formation of granuloma at the superior end of the prosthesis, and the development of a mucous membrane webbing between the two loops of a stent. Due to the lack of long-term follow-up, this technique is reserved for the treatment of severe tracheal stenosis with cartilage impairment in patients who have contraindications for external reconstructive surgery.

Aged↗
PubMed1996

The MS-MS determination of the fragmentation pathways of some substituted 1,2,3-benzotriazin-4-ones with possible applications in metabolic studies.

1,2,3-Benzotriazin-4-one derivatives are extensively used as herbicides, insecticides and nematicides. Incorporation of these compounds into the human food chain is a cause for concern, since their toxicity to man is well documented. This work describes the development of a data-base of classical 1,2,3-benzotriazin-4-one fragmentation patterns and consequent sequential neutral mass losses which allows the prediction of the presence of a triazinone derived compound. Positive and negative ion tandem mass spectrometry techniques were employed since they allow rapid and sensitive structural characterization of drugs and their metabolites in biological fluids through the unambiguous monitoring of daughter ions from pre-selected primary ions.

Insecticides↗