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Biomedical subjects

N B Powell

Publications and source records attributed to N B Powell.

At least 55 records · Page 3Linked to original sources
PubMed1993

Localization of the meningococcal receptors for human transferrin.

The interaction between gold-labelled human transferrin (Au-HTF) with live meningococci after growth in vivo or in different in vitro conditions was examined by electron microscopy to localize and quantify the numbers of HTF-binding sites on the cell surface. It was clearly demonstrated that HTF binds to the surface of live meningococci (of different serogroups and serotypes) after growth in either iron-sufficient or iron-restricted cultures, although the degree of labelling was always higher (2- to 35-fold) in the latter case. The commensal Neisseria polysaccharea behaved similarly. Ultrathin sections showed that Au-HTF was localized predominantly on the outer membrane of the cells and vesicles, with hardly any internalization. Au-HTF labelling on meningococci was significantly reduced after incubation with unlabelled HTF or with rabbit antiserum containing antibodies against transferrin-binding proteins (TBPs), demonstrating the specificity of the interaction. These sera also blocked binding between HTF and outer membrane proteins on Western immunoblots. Direct evidence of the expression of the TBPs (Western blots) and localization of the HTF receptor (electron microscopy) on in vivo-grown meningococci was obtained from organisms derived without laboratory culturing from the cerebrospinal fluid of a patient. There was considerable cell-to-cell variation in the amount of labelling present on cells of the same sample (in vitro- or in vivo-grown organisms) and between different strains. The degree of binding varied with time of incubation of the cells with Au-HTF. The gold particles frequently formed discrete circles on the cell surfaces of the in vitro-grown organisms; these circles appear to be associated with outer membrane vesicle formation. The results show that the TBPs, which form part of the active components of the HTF receptor(s), are expressed in vivo and are surface exposed and immunogenic and that antibodies against them can interfere with the HTF binding of the meningococcal cells, which may affect iron utilization. This study further supports the concept of regarding the TBPs as future vaccine candidates.

Animals↗
PubMed1993

Obstructive sleep apnea syndrome: a review of 306 consecutively treated surgical patients.

Three hundred six consecutively treated surgical patients with obstructive sleep apnea syndrome were evaluated from a group of 415 patients. One hundred nine patients were excluded because they failed to obtain a postoperative polysomnogram or were lost to followup. All patients received a physical examination, cephalometric analysis, fiberoptic examination, and polysomnography before treatment to document OSAS and determine the areas of obstruction. A two-phase surgical protocol was used for the reconstruction of the upper airway. Phase I surgery consisted of a uvulopalatopharyngoplasty (UPPP) for palatal obstruction and genioglossus advancement with hyoid myotomy-suspension for base of tongue obstruction. Failures of phase I were offered phase 2 reconstruction, which consisted of maxillary-mandibular advancement osteotomy. One hundred twenty-one patients were treated with nasal continuous positive airway pressure (CPAP) before surgery and this was the primary method of evaluating surgical success. Results were reported on the polysomnogram performed a minimum of 6 months after surgery and compared to the preoperative polysomnogram and the second night nasal CPAP study. The polysomnographic results included respiratory disturbance index (RDI), lowest oxyhemoglobin saturation (LSAT), and sleep architecture parameters. Surgery was considered a success if it was equivalent to nasal CPAP or the postoperative RDI was less than 20 with normal oxygenation. The overall success rate, which included patients that dropped from the protocol, was 76.5%, with a mean followup of 9.3 months (SD, 6.7). The preoperative RDI, nasal CPAP RDI, and postoperative RDI were 55.8 (SD, 26.7), 7.2 (SD, 5.4), and 9.2 (SD, 7.5), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Maxillary, mandibular, and hyoid advancement for treatment of obstructive sleep apnea: a review of 40 patients.

Forty patients with documented obstructive sleep apnea syndrome (OSAS) were evaluated following maxillary and mandibular osteotomies (MMO). All patients were evaluated before and after surgery by a physical examination, fiberoptic pharyngoscopy, cephalometric analysis, and polysomnography. Ninety-seven percent of the patients responded to the surgical treatment, based on the polysomnogram. The present indications for MMO are severe OSAS, morbid obesity, and severe mandibular deficiency.

Adolescent↗
PubMed1990

Maxillofacial surgery and nasal CPAP. A comparison of treatment for obstructive sleep apnea syndrome.

Nasal continuous positive airway pressure (CPAP) is the primary therapy for obstructive sleep apnea syndrome (OSAS). Recent reports have indicated, however, that there is a small but significant number of failures related to patient compliance. Primary surgical treatment, which has been uvulopalatopharyngoplasty (UPPP), has declined because of poor results. A reviewed of UPPP failures has shown that while UPPP eliminated palatal obstruction, it failed to eliminate base of tongue obstruction. Maxillofacial surgery has been reported as treatment of OSAS by correcting base of tongue obstruction. Thirty patients with severe OSAS were evaluated to compare nasal CPAP and maxillofacial surgery. The goal was to determine if our surgical protocol was as effective as nasal CPAP. All patients initially underwent baseline diagnostic polysomnography to document OSAS. A nasal CPAP study was performed to determine the appropriate positive end-expiratory pressure. The patients in this study were using nasal CPAP, but they found it unacceptable as long-term treatment and elected surgery. Maxillofacial surgery consisted of maxillary, mandibular, and hyoid advancement. Polysomnography was performed six months following surgery and compared with the night 2 CPAP results. The parameters included in the investigation were the respiratory disturbance index (RDI), lowest SaO2, number of SaO2 falls below 90 percent, total sleep time (TST), REM sleep percent, stage 3-4 sleep percent, and wake after sleep onset. The mean RDI before treatment was 72.0 (SD 25.7). After completing therapy, the RDI from surgery and CPAP was 8.8 (SD 6.0) and 8.6 (SD 4.1), respectively. The mean low SaO2 prior to treatment was 61.0 (SD 13.5), and the CPAP results and postsurgical results were 86.2 (SD 5.5) and 86.1 (SD 4.2), respectively. An analysis of variance was used to examine the results, and there was no statistical difference between nasal CPAP and surgery for all respiratory variables.

Adult↗
PubMed1990

Maxillofacial surgery and obstructive sleep apnea syndrome.

Maxillofacial surgery has proven to be an effective method for controlling OSA syndrome, and its results are as effective as those obtained with nasal CPAP. The presurgical evaluation, which includes polysomnography, physical examination, fiberoptic pharyngoscopy, and cephalometric analysis, is essential in directing surgical therapy. With phased reconstruction of the upper airway there is an excellent chance of correcting the obstructive process and eliminating the associated problems of OSA syndrome.

Adult↗
PubMed1989

Pericranial free grafts in the face.

The pericranium is a thin connective tissue coating of the neurocranium that can be used as a free graft for selected facial surgery. To assess the potential use of this graft in the face, we describe our experience over a period of 33 months on 34 patients. Eighty-two individual pericranial grafts were used, with an average of 2.4 grafts per patient. The pericranium was used for augmentations, coatings, and suspensions, with the latter two proving to be the most useful. Like other autogenous grafts, the pericranium may eventually undergo some resorption; however, with experience, overcorrection can be planned. The graft is convenient and easy to harvest, with little or no defect at the donor site. With a mean follow-up of 13.6 months, rejection or infection has not been experienced to date.

Adolescent↗
PubMed1989

Facial contouring with outer-table calvarial bone. A 4-year experience.

The long-term fate of outer table calvarial bone has not been previously well established in terms of graft resorption and resultant contour in the face. A 4-year experience is presented with an emphasis on these areas. Eight hundred fifty grafts were placed in the face on 170 patients during this study period. A subgroup consisting of the nasal region was selected for a detailed analysis, since this complex could be readily evaluated, and the results have paralleled the remaining group. Although partial resorption is seen at most sites, ranging from insignificant to 30%, excellent contour has been achieved throughout the face and maintained in all but a few cases. The areas of maximum resorption and contour change were seen at the nasal dorsum and lateral posterior mandible.

Adult↗
PubMed1989

Inferior mandibular osteotomy and hyoid myotomy suspension for obstructive sleep apnea: a review of 55 patients.

Fifty-five patients with obstructive sleep apnea syndrome (OSAS) were evaluated following inferior mandibular osteotomy with hyoid myotomy and suspension. Patients were objectively examined by polysomnography before and 6 months following the surgical procedure. Thirty-seven patients (67%) had a good response from surgery, and 18 patients (33%) were considered nonresponders. Lung disease, mandibular deficiency, and obesity were factors found to affect the success of surgical treatment.

Adult↗
PubMed1989

Maxillofacial surgery and obstructive sleep apnea: a review of 80 patients.

To determine the effectiveness of the surgical treatment of obstructive sleep apnea, we retrospectively evaluated 80 patients. One group consisted of 55 patients who had undergone a limited osteotomy of the anterior mandible: inferior sagittal osteotomy with hyoid myotomy and suspension. Important criteria for the selection of these patients were normal pulmonary function, normal mandibular skeletal development, and the absence of morbid obesity. Polysomnography revealed that 37 patients (67%) had responded to the surgical treatment and 18 patients (33%) had not. The second group of 25 patients, selected for morbid obesity, severe mandibular deficiency, and failure of other surgical procedures, had undergone maxillomandibular osteotomy with hyoid advancement. All patients in the second group showed good results, as determined by polysomnography.

Adult↗
PubMed1989

Maxillo-mandibular surgery for obstructive sleep apnoea.

Many therapeutic approaches, including mandibular surgery, have been proposed for the treatment of obstructive sleep apnoea syndrome. In the largest study of its type yet reported, 54 patients (population A) underwent mandibular surgery: 36 had palato-pharyngoplasty and inferior sagittal osteotomy of the mandible with hyoid myotomy and resuspension, and 18 (population B) had maxillo-mandibular hyoid advancement, a procedure consisting of palato-pharyngoplasty, inferior sagittal osteotomy of the mandible with hyoid myotomy and, several months later, a maxillo-mandibular osteotomy. Criteria for procedure selection and for evaluation of results were pre-set, and clinical and polygraphic follow-up occurred 6-8 months after final surgery. In population A, 32 of the 36 patients had improved; but only 20 were evaluated as "satisfactory". In contrast, all of the population B patients were judged satisfactory. Four of the population B patients received nasal continuous positive airway pressure (CPAP) before any surgery, and both approaches gave similar good polygraphic results. The degree of skeletal cranio-facial deficiencies, particularly retrognathia, is crucial for procedure selection. We describe potential procedural risks and problems.

Adolescent↗
PubMed1988

A new approach to evaluation and surgery of the malar complex.

Prominent malar eminences are considered aesthetic and have been equated with a more youthful appearance. The precise area for accentuation and the surgical method for altering contour have not been universally agreed upon. A new technique for evaluation is suggested, and a surgical osteotomy for malar contouring is described. Twenty-one patients have undergone treatment; 16 procedures were bilateral and 5 were unilateral. The longest postoperative follow-up is 20 months and the shortest, 6 months. Results have shown symmetry, natural contour, good patient acceptance, and no significant complications. These two new techniques, when combined with existing knowledge and experience, should enhance the ability to analyze and alter the malar complex.

Adolescent↗
PubMed1988

Obstructive sleep apnea, continuous positive airway pressure, and surgery.

Patients with obstructive sleep apnea (OSA) who have undergone upper airway surgery could be expected to improve if surgery alleviated some or all of the anatomic obstructions, or continue to desaturate at preoperative levels if the surgery was not corrective. Factors such as morbid obesity, general anesthesia recovery, and operative edema can potentially cause desaturations below preoperative levels. Because of this risk, patients with severe OSA have been considered for protective tracheostomy. The findings of our study suggest that selected patients who would have been past candidates for protective tracheostomy while undergoing surgery for severe OSA can, as an alternative, be considered for immediate postoperative use of nasal continuous positive airway pressure (CPAP). Ten surgical patients with severe OSA who elected surgical treatment were successfully treated with CPAP immediately after extubation and postoperatively to assist with airway patency and hemoglobin saturation. Postoperative followup included monitoring of continuous pulse oximetry, cardiac activity, and intermittent arterial blood gases. Preoperatively, all ten patients had marked decrease in oxygen desaturation levels during sleep, with a mean nadir oxygen saturation (SaO2) to 51.5%. After surgery, all patients in this group maintained SaO2 levels to no lower than 90%, with a mean SaO2 level of 93% while using CPAP on room air (F10(2) 21%) only.

Adult↗
PubMed1987

Cranial bone grafting in facial aesthetic and reconstructive contouring.

Harvesting of outer-table cranial bone for major craniofacial surgery can be an extensive surgical undertaking. However, when it is used for facial cosmetic and reconstructive contouring, it can be a relatively minor procedure. Our experience with harvesting outer-table calvarial bone and its placement in the face will support a more liberal use of this material. Over a period of 24 months, we have performed outer-table calvarial bone grafts on 62 patients, totaling 367 individual grafts, which were placed in an average of three separate facial sites per patient. The grafts have been easily taken in a prompt fashion with little postoperative discomfort or graft-site deformity. We have not experienced significant complications in harvesting or in placement of cranial bone. The contour provided in the face is quite natural and predictable.

Adolescent↗
PubMed1986

Maxillary, mandibular, and hyoid advancement: an alternative to tracheostomy in obstructive sleep apnea syndrome.

Nine patients with severe obstructive sleep apnea syndrome (OSAS)--for whom several therapeutic approaches, including palatopharyngoplasty, had failed--were treated with a combined maxillary, mandibular, and hyoid advancement. Objective evaluation--performed before and 4 to 18 months after surgery, using nocturnal polysomography--indicated that the OSAS had improved or had disappeared. This surgical approach is beneficial for specific cases of OSAS, which can be identified by mandatory presurgical tests.

Female↗