Examining evidence of reproductive isolation in sockeye salmon.
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Animals↗
Biomedical subjects
D J Howard
Publications and source records attributed to D J Howard.
Reproductive processes in two oak (Quercus) contact zones with different levels of hybridization.
Patterns of reproductive isolation between two sympatric species of oaks, Quercus gambelii and Q. grisea, that exhibit strong ecological differentiation were examined. A full diallel cross using four trees of each species (i.e. all possible pollinations among eight trees) was performed. This design was repeated at two sites that represent different outcomes of sympatry: (1) a xeric mountain ridge where many hybrids are established (HZ); and (2) a mesic valley bottom where virtually no hybrids are established (MOCYN). By measuring fruit survival at several developmental stages, both the timing and strength of reproductive barriers within and between sites, species, cross types, and pollen dosage levels were examined. In three of four cases, heterospecific fruit set was significantly reduced compared to conspecific fruit set. This reduction occurred after the time of fertilization, but before the onset of embryo growth. Increasing the dose of pollen from an average of 9-194 grains/stigma did not affect this result. Thus, early postfertilization processes play a strong role in species fidelity in these oaks. Quercus gambelii experienced a five-fold decrease in conspecific fruit set at HZ relative to MOCYN. In contrast, heterospecific fruit set of Q. gambelii was the same at both sites. Poor Q. gambelii pollen performance is implicated as playing the major role in this result. One Q. gambelii individual at HZ was highly fecund, and had higher heterospecific than conspecific fruit set; slight introgression in this tree was detected uisng RAPD markers. The Environmental Emasculation Hypothesis that posits that environmental stress can increase the probability of hybrid formation by reducing the competitive ability of male gametes of one species is proposed.
Crosses, Genetic↗
Spatio-temporal dynamics of the Allonemobius fasciatus- A. socius mosaic hybrid zone: a 14-year perspective.
Long-term studies of hybrid zones can provide valuable insight into a number of questions that have long attracted the attention of evolutionists. These questions range from the stability and fate of hybrid zones to the relative fitness of hybrids. In this paper we report the results of a 14-year survey of the Allonemobius fasciatus-Allonemobius socius hybrid zone. Populations were collected intensively in 1986 and 1987 and then more sporadically through the end of the 1980s and throughout the 1990s. By documenting changes in the genetic composition of populations near and within the zone during this period of time we assessed: the strength of the reproductive isolation between the two species; the relative growth rates (which can be considered a surrogate of relative fitness) of genotype classes corresponding to hybrids and to pure species individuals; and, the power of single-year and multi-year measurements of relative growth rates to predict changes in the genetic composition of mixed populations through time. In brief, we found very large year-to-year variation in the relative growth rates of pure species and hybrid individuals. This variation may reflect the fact that both species are at the edge of their range and perhaps at the limits of their ability to deal with environmental perturbations. As a consequence of the variation, even multi-year estimates of relative growth rates often provided imprecise predictions regarding the future genotypic composition of mixed populations. Despite our limited ability to predict the dynamics of individual populations, some trends are apparent. A. socius, the southern species, has clearly increased in frequency along a transect through the Appalachian Mountains, indicating that the zone is moving north in this region. In contrast, the zone appeared to be more stable along the East Coast transect. Within mixed populations, character-index profiles are often bimodal and stable through time, indicating relatively strong reproductive isolation between the two species that is not being reinforced, nor is it breaking down.
Alleles↗
Recurrence and its avoidance in juvenile angiofibroma.
OBJECTIVE: Angiofibroma is a highly vascular lesion for which a wide range of surgical approaches has been recommended. Irrespective of the approach, a significant and often rapid recurrence rate is reported in all major series. AIM: To consider the impact of lessons learned from imaging on the recurrence rate of angiofibroma. MATERIAL AND METHODS: From a cohort of 90 male patients with histologically proven angiofibroma, 40 individuals were studied. The recurrence rate in 20 cases treated before March 1998 was compared with that in 19 cases treated thereafter. In the latter group, an additional exploration of the basisphenoid had been undertaken. RESULTS: The two cohorts were comparable in age range (7-27 y and 11-24 years, respectively), and all had been treated by midfacial degloving. In the first group, 8 recurrences occurred which were multiple in 1 patient. In the next 19 patients, the area of the pterygoid canal was meticulously explored and the basisphenoid drilled to remove all residual tumor. No recurrences have occurred in this group during a follow-up of between 6 months to 3 years. CONCLUSION: Meticulous removal of angiofibroma infiltrating the pterygoid canal and basisphenoid is paramount to avoid "recurrence."
Adolescent↗
The laryngeal mask airway in tonsillectomy: the surgeon's perspective.
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Humans↗
Laryngeal chondrosarcoma: a 24-year experience at the Royal National Throat, Nose and Ear Hospital.
This paper presents a review of the experience of 12 patients with chondrosarcoma of the larynx treated at The Royal National Throat, Nose and Ear Hospital, London, over the last 24 years. This represents the largest European series and the third largest in the world. Chondrosarcoma is the most frequent non-epithelial malignant tumor of the larynx, with 83.3% of cases arising from the cricoid cartilage in our series. We have shown that deep wedge biopsy with a CO2 laser, aided by computerized tomography scanning, gives the most reliable diagnosis. Laryngeal chondrosarcoma is characterized by indolent growth, a potential for local recurrence and, infrequently, by metastases. The treatment details of our patients are discussed. Adequate partial resection is often successful and use of CO2 laser as the initial treatment in five of these cases is presented.
Adult↗
The role of partial laryngeal resection in current management of laryngeal cancer: a collective review.
A spectrum of treatment plans and surgical procedures is available for management of early and moderately advanced laryngeal cancer. While the approach of chemotherapy and irradiation, or irradiation alone, followed by total laryngectomy for failure is often employed in practice by present day clinicians, the options of conventional conservation surgery (CCS), transoral endoscopic laser surgery (TLS) and supracricoid partial laryngectomy (SCPL) provide a wide choice of treatments that may help attain the goal of cure with preservation of laryngeal function and integrity of the airway. While CCS has been supplanted for many early-stage lesions by TLS and for more advanced stages by SCPL, centres throughout the world have reported favourable results with CCS, which is often modified to include resection of more extensive tumours than was previously possible. During the past decade a number of extended CCS procedures have been developed for management of glottic tumours involving both vocal cords and the anterior commissure, the paraglottic space and with vocal cord fixation, and for supraglottic tumours involving the glottis or hypopharynx. TLS has proved an effective, minimally invasive and functionally satisfactory procedure for management of suitable T1 and T2 glottic cancers, and stage I-III supraglottic cancers. The procedure may be effectively employed in combination with neck dissection and postoperative radiotherapy when necessary, particularly for moderately advanced supraglottic carcinomas. SCPL has proven effective in management of glottic and supraglottic cancers of all stages, even with involvement of paraglottic space and thyroid cartilage, provided at least one arytenoid unit can be preserved with clear margins. Invasion of cricoid cartilage is the most significant limitation for this procedure. All three surgical approaches have been employed for irradiation failure, but with greatly increased failure and complication rates compared with the results of treatment of non-irradiated patients. Thus a decision to treat laryngeal cancer initially with irradiation may preclude a satisfactory result from partial laryngectomy should radiation fail. The treatment of laryngeal cancer should be individualized according to the size and extent of the tumour, the age and physical condition of the patient, and the skill and experience of the surgeon with various treatment modalities and surgical procedures.
Combined Modality Therapy↗
Prevention before cure.
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Carcinoma, Squamous Cell↗
A third decade's experience with the gastric pull-up operation for hypopharyngeal carcinoma: changing patterns of use.
Gastric transposition has been used extensively in this department since 1965 for reconstruction following pharyngolaryngoesophagectomy (PLO). A previous report by Harrison and Thompson in 1986 detailed our experience with 101 cases dating back to 1965. Here we review our experience between 1986-1996. Medical records of 41 cases were examined. The primary site and stage of tumour and associated lymph nodes, patient demographics, complications, in-patient mortality and survival as demonstrated by the Kaplan-Meier method were recorded. Gastric transposition is now used for more extensive tumours: 70 per cent T4 (83 per cent pathologically T4) compared to 21 per cent in the previous report. A high proportion of 'radiation failures' remains (54 per cent). The in-hospital mortality has fallen from 11 per cent to seven per cent. The five-year-survival calculated using the Kaplan-Meier method is 11 per cent. This procedure is increasingly being used as a palliative procedure aiming to restore swallowing in the relatively young patient who has very extensive hypopharyngeal carcinoma. Long-term survival rates specific to this operation have fallen. This is attributed to patient selection for the procedure with the vast majority having disease extending into bone, cartilage or soft tissues (T4). The defect created by the resection of less extensive tumours are now increasingly reconstructed with jejunal free flaps and musculocutaneous flaps.
Adult↗
The role of midfacial degloving in modern rhinological practice.
The midfacial degloving approach has been available for twenty five years and is slowly increasing in popularity in the management of extensive benign lesions of the sinonasal region, for selected malignancy in this area and to afford access to the nasopharynx and infra-temporal fossa. The advantages, applications and low complication rate are presented in a cohort of 86 patients, ranging from three to 79 years of age with a mean follow-up of 5.5 years. Seventy-seven per cent of the group had benign pathology of which juvenile angiofibroma was the commonest (40 cases). The 20 cases of malignant disease were a heterogeneous group histopathologically including adenoid cystic carcinoma (four cases), malignant schwannoma (two cases), rhabdomyosarcoma (two cases) and squamous cell carcinoma (two cases). Five underwent bilateral radical maxillectomies combined with orbital clearance in one patient. Complications include oro-antral fistula (three cases) and epiphora (three cases) all of which were successfully treated.
Adenoids↗
Management options and survival in malignant melanoma of the sinonasal mucosa.
OBJECTIVES/METHODS: To determine whether surgery combined with radiotherapy confers any survival benefit on radical local excision alone in the management of mucosal malignant melanoma of the nose and sinuses. STUDY DESIGN: Retrospective review. METHODS: From a cohort of 72 patients treated between 1963 and 1996 within a single unit, complete data were available for 58 individuals who were examined to determine whether there was any significant statistical difference in local control and/or survival between those receiving surgery and those receiving combined surgery and radiotherapy. RESULTS: There were 30 men and 28 women. Their ages ranged from 39 to 90 years (mean, 64 y). Twenty-nine patients underwent surgery alone; 23 patients underwent surgery and radiotherapy; 6 patients received surgery and chemotherapy; and 3 patients received surgery, chemotherapy, and radiotherapy. Primary surgery included lateral rhinotomy (42 cases), maxillectomy (8 cases [orbital clearance in 3 cases]), craniofacial resection (3 cases), total rhinectomy (3 cases), and endoscopic clearance (2 cases). Survival ranged from 1 to 228 months with rapid patient loss due to local (and/or systemic) disease during the first 36 months, irrespective of the treatment modality. Overall 5-year actuarial survival was 28%, and overall 10-year actuarial survival 20%, with a median survival of 21 months. There was no statistical difference in local control or survival between patients receiving surgery alone and those receiving surgery and radiotherapy, irrespective of whether this treatment was given in the early part of the series (i.e., before 1983) or thereafter. The addition of chemotherapy had no impact on survival, nor did the site of the tumor, the surgical procedure, the presence of lymph node metastases or the age of the patient. CONCLUSION: In this large cohort of sinonasal melanoma, overall survival was poor and did not appear to be improved by the addition of radiotherapy.
Adult↗
Synovial chondromatosis in raptors.
Fourteen raptors, consisting of 13 great horned owls (Bubo virginianus) and one red-tailed hawk (Buteo jamaicensis), from central and north central Minnesota, western Wisconsin, and eastern South Dakota (USA) were admitted to a raptor rehabilitation center between June 1992 and June 1995, with perisynovial and synovial chondromatosis affecting multiple joints. Birds were severely debilitated primarily due to loss of shoulder motion. The etiology of these lesions in raptors is unknown.
Animals↗
Oxidative DNA damage in mouse heart, liver, and lung tissue due to acute side-stream tobacco smoke exposure.
Environmental tobacco smoke (ETS) is a hotly debated social, political, and scientific issue, pitting smokers' rights against the health and safety of nonsmokers. Striking an acceptable balance between the two depends largely on the potential health hazard assessment of ETS. Studies from this laboratory have shown that exposure to side-stream cigarette smoke (SSS), the major component of ETS, significantly increases oxidative stress in mouse heart, liver, and lung tissues. This study measures the level of oxidative damage to mouse liver, lung, and heart DNA as a result of this oxidative stress. Adult female Balb/c mice were exposed to a regimen consisting of sequences of a 30-min exposure followed by a 90-min nonexposure. This regimen was performed once for the single exposure and repeated three times for the triple exposure. The heart, lung, and liver were excised from the mice, and DNA was extracted and analyzed for the presence of the oxidative product 8-hydroxy-2'-deoxyguanosine (8-OHdG). In all three tissues, the exposure increased the presence of 8-OHdG above the control levels. In some instances, the increased levels returned to normal by the end of the nonexposure period, while other tissues showed a further increase following nonexposure. These studies demonstrate that limited exposure to SSS produces measurable DNA oxidative damage.
8-Hydroxy-2'-Deoxyguanosine↗
Craniofacial resection for tumors of the nasal cavity and paranasal sinuses--a 17-year experience.
BACKGROUND: The rarity of sinonasal tumors has precluded long-term follow-up of large series of craniofacial resections until now. METHODS: A series of 209 patients suffering from a wide range of histologies who had undergone craniofacial resection for sinonasal neoplasia with up to 17 years' follow-up were analyzed. RESULTS: An overall actuarial survival of 51% at 5 years and 41% at 10 years was found for the cohort as a whole. For malignant tumors, the 5-year actuarial survival was 44%, falling to 32% at 10 years. For benign pathology, the actuarial survival was 75% at both 5 and 10 years. Statistical analysis identified three factors which significantly affect outcome and survival: malignant histology, brain involvement, and orbital involvement. Few complications are associated with the surgery, with the mean post-operative stay being 16 days. CONCLUSIONS: The improved survival and minimal morbidity and mortality associated with craniofacial resection make it the optimum approach to sinonasal tumors.
Actuarial Analysis↗
Environmental tobacco smoke in the workplace induces oxidative stress in employees, including increased production of 8-hydroxy-2'-deoxyguanosine.
Environmental tobacco smoke (ETS) is a pervasive contaminant in the workplace. Our objective was to determine the oxidative stress effects of ETS on employees who are exposed. The results provide information that is useful to the resolution of risk assessment questions associated with ETS. We analyzed two blood draws from volunteers in our control and exposed groups. The level of exposure to ETS was determined through plasma cotinine measurements, which showed a 65% increase from the control group to the exposed group. Exposure to ETS resulted in a statistically significant increase of 63% of the oxidative DNA mutagen 8-hydroxy-2'-deoxyguanosine in the blood of exposed subjects. This oxidative DNA damage has been linked to an increased risk of developing several degenerative chronic diseases, including coronary heart disease and cancer. The exposed subjects also had increased levels of superoxide dismutase, catalase, glutathione peroxidase (GPOX), and glutathione reductase. However, these increases were only statistically significant in catalase and GPOX. Catalase levels were 13% higher in the exposed group, and GPOX levels were 37% higher in exposed volunteers. The biochemical evidence suggests that exposure to ETS causes oxidative stress, resulting in DNA damage that may increase the risk of certain diseases.
8-Hydroxy-2'-Deoxyguanosine↗
Oxidative stress induced by environmental tobacco smoke in the workplace is mitigated by antioxidant supplementation.
Environmental tobacco smoke (ETS) is a pervasive contaminant in the workplace. Previous studies by this laboratory have shown that exposure to workplace ETS results in increased oxidative stress and damage, as measured by increased levels of the antioxidant enzymes superoxide dismutase, catalase, glutathione reductase, and glutathione peroxidase. 8-Hydroxy-2-deoxyguanosine, a marker of oxidative DNA damage, was also 63% greater in the exposed group compared with controls. Subjects in the previous study who reported workplace exposure to ETS were given a 60-day supply of an over-the-counter antioxidant formulation consisting of 3000 microg of beta-carotene, 60 mg of vitamin C, 30 I.U. of alpha-tocopherol, 40 mg of zinc, 40 microg of selenium, and 2 mg of copper. After the 60-day supplementation period, blood samples were again drawn, and the results were compared with the presupplementation values. A 62% decrease in 8-hydroxy-2-deoxyguanosine was observed after supplementation. Lipid peroxidation levels were also decreased, as were the antioxidant enzyme activities. The biochemical evidence suggests that exposure to ETS in the workplace increases oxidative stress and that antioxidant supplementation may provide some protection.
Adult↗
Closure of the nasal cavities in the treatment of refractory hereditary haemorrhagic telangiectasia.
From a cohort of 35 patients with hereditary haemorrhagic telangiectasia (HHT), 12 patients have undergone closure of the one or both nasal cavities during the last three years for refractory epistaxis. All had failed other forms of treatment including hormone therapy, laser coagulation and septodermoplasty. All patients were available for follow-up at six months or longer. In all patients where complete closure was achieved (11 out of 12) bleeding ceased completely from the operated side.
Adult↗
A retrospective study of the role of the argon laser in the management of epistaxis secondary to hereditary haemorrhagic telangiectasia.
Epistaxis is a common symptom in patients with hereditary haemorrhagic telangiectasia. It may vary in severity from infrequent mild bleeds to regular severe bleeding, the latter requiring multiple blood transfusions. Laser, which can be used to coagulate the telangiectasia without destroying the overlying nasal mucosa, would theoretically seem to be the ideal mode of treatment. In this pilot study, an argon laser has been used on nineteen patients with hereditary haemorrhagic telangiectasia and is shown to be beneficial in patients with mild or moderate epistaxis. Patients with severe epistaxis, or who fail argon laser treatment, are candidates for alternative therapeutic strategies such as a modified Young's procedure.
Adolescent↗