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Biomedical subjects

W Lawson

Publications and source records attributed to W Lawson.

At least 37 records · Page 2Linked to original sources
PubMed1996

Employment patterns after successful kidney transplantation.

We studied 822 kidney transplant recipients followed 1-9 years to determine the dynamics of their entering and leaving the work force. Multivariate analysis revealed that not being diabetic and that being employed pretransplant were associated with a higher rate of posttransplant employment. Some recipients in all pretransplant employment categories, including those receiving disability benefits pretransplant, returned to full-time work posttransplant. The most rapid return to work was in those who had been working full-time or attending school pretransplant. After returning to work, a higher percentage of diabetic recipients stopped working; of those who stopped working, 50% received disability benefits. In contrast, nondiabetic recipients who stopped working full-time were more likely to be retired or working part-time; only 22% received disability benefits.

Adult↗
PubMed1996

Anthropometric analysis of the female Latino nose. Revised aesthetic concepts and their surgical implications.

OBJECTIVE: To determine whether the present aesthetic concepts set forth for rhinoplasty in white patients can be applied to the ethnic variations seen in Latino women and, if not, to develop a reproducible means of analysis to serve as a guide for surgical correction. DESIGN: Cohort analytic study; criterion standard analysis of nasal aesthetics. PARTICIPANTS: Ninety-seven Latino women and 40 white women. INTERVENTIONS: Patients were separated according to geographic area of origin, either the Caribbean, Central America, or South America. Anthropometric measurements were obtained and nasal indexes were calculated. Results were compared with previously reported data for African Americans and whites. All patients underwent complete nasal photographic analysis. RESULTS: Caribbean subjects showed the greatest divergences from whites and resembled African-American anthropometric norms, whereas Central and South American subjects more closely resembled white norms. Two new aesthetic concepts were developed, the dorsal nasal breakpoint and the horizontal nasal axis, which have implications for aesthetic rhinoplasty. The breakpoint is a pivotal point along the nasal dorsum, structurally determined, which was found at different locations in all the groups studied. Caribbean subjects had breakpoints approximately halfway down the dorsum. Central and South Americans had breakpoints about two thirds of the way down the dorsum, and whites had breakpoints three fourths of the way down the dorsum. The horizontal rotation axis is present along a plane that connects the top of the ala with the tip. Rotation of the tip about this axis affects both the characteristics of the dorsal breakpoint and the final appearance of the nose. CONCLUSIONS: In general, Latino noses can be anthropometrically categorized as mesorrhine. When the geographically derived groups were examined individually, the Latino nose ranged from subplatyrrhine to paraleptorrhine. Surgical correction should be individualized, as each group requires correction of different nasal features. The dorsal breakpoint and the horizontal axis plane can act as nasal profile guides for surgical modifications that would achieve the current concept of the aesthetic nose.

Adult↗
PubMed1996

Differential regulation of melatonin receptors in sheep, chicken and lizard brains by cholera and pertussis toxins and guanine nucleotides.

G-proteins define both the pharmacological characteristics and the signalling pathways of G-protein-coupled receptors. Melatonin receptors have been shown to belong to this class of receptors through their sensitivity to modulators of G-protein function. This study reveals that 2-125I-iodomelatonin (125I-MEL) binding to different target tissues is differentially affected by agents which disrupt the G-protein cycle. GTP gamma S, pertussis (PTX) and cholera (CTX) toxins each reduce 125I-MEL binding to ovine pars tuberalis (oPT) and lizard brain membranes, whereas chicken brain is affected only by GTP gamma S (guanosine 5'-O-(3-thiotriphosphate)) and CTX. In contrast, high affinity binding of 125I-MEL in the ovine hippocampus was not affected by any of these agents. This finding, together with the fact that neural binding sites of the sheep brain were found to have markedly lower molecular mass than those of the oPT on native gel electrophoresis (365 vs 525 kDa), suggests that the neural 125I-MEL binding sites in sheep may not be G-protein coupled. Pharmacologically, however, the binding sites in the hippocampus and oPT could not be distinguished using 11 analogues of melatonin. Therefore, these data support the notion not only of multiple forms of melatonin receptor/G-protein complex, but of high affinity binding sites for 125I-MEL which do not display sensitivity to guanine nucleotides.

Animals↗
PubMed1996

Gaseous dynamics of the rabbit maxillary sinus.

To better understand the mechanisms underlying maxillary sinus function, the gas composition of the sinus antrum in spontaneously breathing and tracheotomized rabbits (n = 17) was compared. The gas composition of samples (n = 117) obtained from rabbit maxillary sinuses was determined by gas chromatography. Results demonstrated significant differences (P < .005) in sinus gas composition between nasal breathing and tracheotomized animals for oxygen (02) and carbon dioxide (CO2). In tracheotomized animals O2 levels decreased while CO2 levels increased markedly to suprasystemic levels. This unexpected finding may be due to reduced sinus blood flow and the effects of nasal versus tracheal respiration. We conclude that the gaseous dynamics and perhaps the function of the maxillary sinus vary under different respiratory conditions. A better understanding of these processes may lead to earlier diagnosis and the development of improved treatments for sinus disease.

Animals↗
PubMed1996

Management of embossment following the frontal osteoplastic operation.

The deformity in the bony contour of the forehead following the osteoplastic flap procedure on the frontal sinus, termed embossment, occurs in a small but definite number of cases. This complication arises from the combined processes of resorption and deposition of bone following disturbance of the periosteum in performing the operation. A simple and highly reliable method of cosmetic correction employing acrylic cranioplasty has been successfully utilized in a series of cases without complications. The details of the operative technique will be outlined.

Bone Cements↗
PubMed1996

The silicone columellar strut.

The placement of a silicone columellar strut serves to correct columellar retraction, to improve the nasolabial angle, and to increase tip projection by elevating the medical crura of the lower lateral cartilages. The potential complications of extrusion, infection, and migration are minimal if the implant is placed in a separate watertight compartment with a tension-free closure and no impingement of the nasal dome.

Female↗
PubMed1995

Role of the argon beam coagulator in facial rejuvenation surgery.

OBJECTIVE: To compare the hemostatic effectiveness of a new electrosurgical unit, the argon beam coagulator, with current methods of electrocoagulation. DESIGN: A nonrandomized control trial of 20 patients undergoing rhytidectomy. SETTING: Two academic tertiary referral medical centers. PARTICIPANTS: Twenty male patients having moderate to major degrees of facial ptosis. INTERVENTION: All 20 patients underwent a standard rhytidectomy with hemostasis provided by the argon beam coagulator on the right side and conventional electrocoagulation on the left side. OUTCOME MEASURES: Improved hemostasis with minimal depth of injury, length of procedure, decreased blood loss, edema, and ecchymosis, and the ability to coagulate indiscriminately around and over neural tissue without damage (all listed in the literature as advantages of the argon beam coagulator). RESULTS: Poor hemostatic ability was observed with concomitant increased incidence of blood loss, edema and ecchymosis, major hematoma, and length of surgery. Also noted were increased rates of flap compromise and the potential for damage to vital neural structures. CONCLUSION: Our results do not agree with the list of advantages attributed to the argon beam coagulator in the literature.

Aged↗
PubMed1995

Reduction columelloplasty. A new method in the management of the nasal base.

The nasal base is very complex secondary to the dynamic relationship between the skin, underlying muscle, and cartilaginous structures. Recently, we have employed a new method for refinement of the nasal base, which we name reduction columelloplasty. This procedure employs a full-thickness diamond-shaped tissue excision between the feet of the medial crura. The incision is carried down through the skin, depressor septi muscle, and adjacent soft tissue. Following en bloc removal, the defect is carefully closed in a vertical orientation, approximating the medial crura of the lower lateral cartilages. As in the open rhinoplasty approach, the scar produced by this technique is of negligible importance if it is closed using proper techniques of skin eversion and early suture removal. We have found this procedure to be an extremely reliable method for narrowing splayed medial crura, increasing the nasolabial angle, modifying the shape of the nares, and for increasing tip projection.

Cartilage↗
PubMed1995

Melatonin receptors couple through a cholera toxin-sensitive mechanism to inhibit cyclic AMP in the ovine pituitary.

The nature of melatonin receptor-G-protein coupling in ovine pars tuberalis (PT) cells of the pituitary was addressed using cholera (CTX) and pertussis (PTX) toxins. ADP-ribosylation of ovine PT membrane proteins using 32P-NAD in the presence of CTX radiolabelled several substrates including 44, 51, and 60 kD proteins. Each were clearly distinct from the 40 kD substrate radiolabelled in the presence of PTX. Acute incubation of PT membranes with either toxin reduced the number of high affinity binding sites for 125I-MEL, although the magnitude of the inhibition was much greater for CTX (56%) than for PTX (20%). A CTX-sensitive component also mediates the inhibition of forskolin-stimulated cyclic AMP accumulation as pre-treatment of PT cells with CTX (5 micrograms/ml) for 16 h blocked this response. Gs alpha is a major substrate for ADP-ribosylation by CTX, and 16 h pre-treatment of PT cells with CTX (5 micrograms/ml) caused a down-regulation of Gs alpha. Northern analysis showed only one major transcript of Gs alpha of about 2 kb, which would encompass all of the known splice variants of the Gs gene. Screening of a cDNA library from ovine PT for Gs-related genes and sequencing of clones, combined with RT-PCR of PT mRNA, revealed no novel products. On this basis it is concluded that the CTX substrate is unlikely to be a novel splice variant or related gene product of the Gs class of G-protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Diphosphate Ribose↗
PubMed1995

Inverted papilloma: a report of 112 cases.

Inverted papilloma is a benign sinonasal tumor which is locally aggressive and has a significant malignant potential. This report updates the experience of the two senior authors, who have treated 112 patients with inverted papilloma at the Mount Sinai Medical Center over a 20-year period. As clinical examination often underestimates tumor extent, preoperative radiographic assessment is of paramount importance in guiding selection of surgical therapy. Complete en bloc excision via lateral rhinotomy and medial maxillectomy was the method of treatment in the majority of patients (84%). In selected patients with limited disease, or in patients who refused en bloc excision, conservative therapy employing intranasal or transantral ethmoidectomy was performed. The recurrence rates for the two groups were 14% and 20%, respectively. Recurrent disease developed throughout the paranasal sinuses, with the maxillary antrum and ethmoid labyrinth constituting the major sites. In two patients presenting with anterior skull base erosion, craniofacial resection was undertaken to eradicate disease. The latter cases underscore the aggressive nature of the tumor if left untreated. The overall rate of squamous carcinoma in this series was 5%. Given the predilection for local recurrence, multicentricity, and the possibility of malignancy, the authors continue to recommend lateral rhinotomy and medial maxillectomy as the standard therapy for the majority of cases. Management principles as well as a review of the literature are discussed.

Carcinoma, Squamous Cell↗
PubMed1995

Pressure measurements in the normal and occluded rabbit maxillary sinus.

Occlusion of the maxillary ostium is considered to be a key factor in the pathogenesis of maxillary sinusitis. In this study, the authors determined the effect of ostial occlusion on pressure in the rabbit maxillary sinus which, like most humans, has only one ostium. We compared pressures in the normal and occluded maxillary sinus and the nasal cavity during spontaneous breathing in anesthetized adult animals. Serial pressure measurements were obtained from sinuses with patent ostia in nasal-breathing rabbits and with occluded ostia in both nasal-breathing and tracheotomized animals. Sinuses with patent ostia showed pressure curves synchronous with the respiratory cycle. Inspiratory and expiratory pressures in the nasal cavity and the sinus were isobaric. Sinuses with occluded ostia initially developed a positive pressure followed by a negative pressure that reached a subatmospheric plateau of -28.2 +/- 7.3 mm H2O (mean +/- standard deviation [SD]) within 20 to 50 minutes. This is the first quantitative study of sinus pressures using the rabbit as an animal model. The findings may contribute to a better understanding of the role of ostial occlusion in the pathogenesis of maxillary sinusitis in humans.

Animals↗
PubMed1994

A systematic approach to functional reconstruction of the oral cavity following partial and total glossectomy.

Mobility, sensation, volume, and to a lesser extent, the shape of the tongue following partial glossectomy are critical elements to the successful rehabilitation of the patient with oral cancer. Our approach to tongue reconstruction is based on the extent and functional status of the residual tongue and whether there is an associated mandibulectomy. Despite the devastating effects of ablative surgery and radiation, the application of available reconstructive techniques can help to improve the quality of life of these patients. Herein, we present a revised classification scheme for tongue defects along with a discussion of the optimal method for reconstruction based on available techniques.

Adolescent↗
PubMed1994

Microvascular free flaps in head and neck reconstruction. Report of 200 cases and review of complications.

OBJECTIVE: Microvascular free-tissue transfer to the head and neck has become an accepted method of reconstruction owing to increased success rates and superior aesthetic and functional results. Although the large number of arteries and veins in the neck make free-flap revascularization easier than in other recipient sites of the body, there are also unique problems that pose significant risks to the success of the procedure. We report our experience with 200 microvascular free flaps performed between 1987 and 1992. SETTING: This study was conducted at a tertiary referral center. PATIENTS: The majority of patients in this series underwent surgery for squamous cell cancer. Approximately 75% of the reconstructions were performed for defects of the oral cavity. There were 120 vascularized bone-containing free flaps for mandibular and midface reconstruction. The remaining 80 soft-tissue flaps were used for a variety of defects ranging from the scalp to the pharyngoesophagus. RESULTS: An overall success rate of 93.5% for free-tissue transfers is reported. Greater experience with this technique has resulted in a reduction and a change in the nature of the complications encountered compared with those seen in the early part of our series. Donor and recipient site complications, including flap failures and anastomotic revisions, are analyzed in detail with respect to age, radiation status, donor site, and whether the ablative procedure was done for a primary or recurrent neoplasm.

Adolescent↗
PubMed1994

Craniofacial resection. An analysis of 73 cases.

OBJECTIVE: To determine the morbidity and mortality associated with a large series of patients undergoing craniofacial resection at one institution. The series is also analyzed with respect to pathology, disease recurrence, and role of adjuvant therapy. DESIGN: Retrospective review with a mean follow-up of 3 years (range, 6 months to 8 years). SETTING: Tertiary care, urban referral center. PATIENTS: The study included 73 consecutive patients (39 male and 34 female). Ages ranged from 13 to 78 years with a mean of 53.1 years. All patients had benign or malignant tumors of the paranasal sinuses. MAIN OUTCOME MEASURES: Morbidity associated with craniofacial resection was categorized as follows: early (within 30 days of surgery) or late (> 30 days); neurologic, ocular, or infectious. RESULTS: Overall morbidity rate was 63%, and the mortality rate was 2.7%. Of the patients who had complications develop, 26 had development of major morbidities and there were two mortalities. The most common complications were transient alteration in mental status (15 patients), diplopia (11 patients), cerebrospinal fluid leak (10 patients), and osteomyelitis of the frontal bone flap (eight patients). CONCLUSIONS: Craniofacial resection is an effective surgical treatment for paranasal sinus tumors. The mortality rate is acceptable and morbidity appears directly related to experience with the procedure. Infectious complications were the most devastating.

Adolescent↗
PubMed1994

Autoradiographic anomaly in 125I-melatonin binding revealed in ovine adrenal.

Conventional in vitro autoradiographical techniques have been used to screen a number of ovine peripheral tissues for the presence of specific 2-[125I]iodomelatonin binding sites. Intense specific labelling (defined as that displaced by 1 microM melatonin) was observed in the adrenal cortex, and less intense specific binding in the spleen. Subsequent attempts to characterize these adrenal binding sites using in vitro binding assays were unsuccessful. The level of specific binding to both crude membranes and to dispersed whole cell preparations was negligible, and was not correlated with increasing protein or cell concentration. Using quantitative in vitro autoradiography, melatonin was found to competitively inhibit 2-[125I]iodomelatonin binding to sections of the adrenal cortex, but with a considerably lower affinity (IC50 of 1 microM) than that obtained for the ovine pars tuberalis (IC50 of 150 pM) under identical conditions. These results suggest that under the conditions of in vitro autoradiography, 2-[125I]iodomelatonin binds to a finite number of non-receptor sites which are restricted to the ovine adrenal gland. The ability to visualize these sites in the present study may arise through the use of an inappropriately high excess of unlabelled melatonin (1 microM). Consequently to avoid this potential problem, non-specific labelling should perhaps more appropriately be defined as binding in the presence of a concentration of melatonin at approximately 100-fold the value of the Kd (i.e. 10 nM).

Adrenal Glands↗