Extra-group mating increases inbreeding risk in a cooperatively breeding bird.

In many cooperatively breeding species, females mate extra-group, the adaptive value of which remains poorly understood. One hypothesis posits that females employ extra-group mating to access mates whose genotypes are more dissimilar to their own than their social mates, so as to increase offspring heterozygosity. We test this hypothesis using life history and genetic data from 36 cooperatively breeding white-browed sparrow weaver (Plocepasser mahali) groups. Contrary to prediction, a dominant female's relatedness to her social mate did not drive extra-group mating decisions and, moreover, extra-group mating females were significantly more related to their extra-group sires than their social mates. Instead, dominant females were substantially more likely to mate extra-group when paired to a dominant male of low heterozygosity, and their extra-group mates (typically dominants themselves) were significantly more heterozygous than the males they cuckolded. The combined effects of mating with extra-group males of closer relatedness, but higher heterozygosity resulted in extra-group-sired offspring that were no more heterozygous than their within-group-sired half-siblings. Our findings are consistent with a role for male-male competition in driving extra-group mating and suggest that the local kin structure typical of cooperative breeders could counter potential benefits to females of mating extra-group by exposing them to a risk of inbreeding.

Environmental constraints influencing survival of an African parasite in a north temperate habitat: effects of temperature on development within the host.

The monogenean Protopolystoma xenopodis has been established in Wales for >40 years following introduction with Xenopus laevis from South Africa. This provides an experimental system for determining constraints affecting introduced species in novel environments. Parasite development post-infection was followed at 15, 20 and 25°C for 15 weeks and at 10°C for ⩾1 year and correlated with temperatures recorded in Wales. Development was slowed/arrested at ⩽10°C which reflects habitat conditions for >6 months/year. There was wide variation in growth at constant temperature (body size differing by >10 times) potentially attributable in part to genotype-specific host-parasite interactions. Parasite density had no effect on size but host sex did: worms in males were 1·8 times larger than in females. Minimum time to patency was 51 days at 25°C and 73 days at 20°C although some infections were still not patent at both temperatures by 105 days p.i. In Wales, fastest developing infections may mature within one summer (about 12 weeks), possibly accelerated by movements of hosts into warmer surface waters. Otherwise, development slows/stops in October-April, delaying patency to about 1 year p.i., while wide variation in developmental rates may impose delays of 2 years in some primary infections and even longer in secondary infections.

Environmental constraints influencing survival of an African parasite in a north temperate habitat: effects of temperature on egg development.

Factors affecting survival of parasites introduced to new geographical regions include changes in environmental temperature. Protopolystoma xenopodis is a monogenean introduced with the amphibian Xenopus laevis from South Africa to Wales (probably in the 1960s) where low water temperatures impose major constraints on life-cycle processes. Effects were quantified by maintenance of eggs from infections in Wales under controlled conditions at 10, 12, 15, 18, 20 and 25°C. The threshold for egg viability/ development was 15°C. Mean times to hatching were 22 days at 25°C, 32 days at 20°C, extending to 66 days at 15°C. Field temperature records provided calibration of transmission schedules. Although egg production continues year-round, all eggs produced during >8 months/ year die without hatching. Output contributing significantly to transmission is restricted to 10 weeks (May-mid-July). Host infection, beginning after a time lag of 8 weeks for egg development, is also restricted to 10 weeks (July-September). Habitat temperatures (mean 15·5°C in summer 2008) allow only a narrow margin for life-cycle progress: even small temperature increases, predicted with 'global warming', enhance infection. This system provides empirical data on the metrics of transmission permitting long-term persistence of isolated parasite populations in limiting environments.

Three-dimensional ultrasound-assisted popliteal catheter placement revealing aberrant anatomy: implications for block failure.

BACKGROUND: The current means of introducing continuous sciatic catheters include nerve stimulation, with or without catheter stimulation techniques. More recently, ultrasound has been utilized to facilitate catheter placement. METHODS: This case represents a stimulating catheter-guided continuous block facilitated by three-dimensional ultrasound, which revealed aberrant anatomy with proximal and wide bifurcation of the sciatic nerve with implications for block failure. RESULTS: Before ultrasound imaging secondary failures were attributed to catheter misplacement or dislodgement. CONCLUSION: Because of this case observation, our current practice is to use ultrasound confirmation of the bifurcation of the nerve of all popliteal catheter placements, particularly catheters placed in patients having ambulatory procedures to prevent secondary failure of catheters at home.

Anatomical suitability of C1-2 transarticular screw placement in pediatric patients.

OBJECT: Craniovertebral instability is a challenging problem in pediatric spinal surgery. Recently, C1-2 transarticular screw fixation has been used to assist in craniovertebral joint stabilization in pediatric patients. Currently there are no available data that define the anatomical suitability of this technique in the pediatric population. The authors report their experience in treating 31 pediatric patients with craniovertebral instability by using C 1-2 transarticular screws. METHODS: From March 1992 to October 1998, 31 patients who were 16 years of age or younger with atlantooccipital or atlantoaxial instability, or both, were evaluated at our institution. There were 21 boys and 10 girls. Their ages ranged from 4 to 16 years (mean age 10.2 years). The most common causes of instability were os odontoideum (12 patients) and ligamentous laxity (eight patients). Six patients had undergone a total of nine previous attempts at posterior fusion while at outside institutions. All patients underwent extensive preoperative radiological evaluation including fine-slice (1-mm) computerized tomography scanning with multiplanar reconstruction to evaluate the anatomy of the C1-2 joint space. Preoperatively, of the 62 possible C1-2 joint spaces in 31 patients, 55 sides (89%) were considered suitable for transarticular screw placement. In three patients the anatomy was considered unsuitable for bilateral screw placement. In three patients the anatomy was considered inadequate on one side. Fifty-five C1-2 transarticular screws were subsequently placed, and there were no neurological or vascular complications. CONCLUSIONS: The authors conclude that C1-2 transarticular screw fixation is technically possible in a large proportion of pediatric patients with craniovertebral instability.

Developing a special needs restraint loaner program for transporting medically fragile children.

Pediatric orthopaedic patients require special consideration for their transportation needs. A hospital-based program to fulfill these needs promotes patient safety and allows accessibility of needed devices to elective and nonelective patients. Nurses can be an integral part of this process. This article presents the process of establishing a special needs restraint program including the legalities, acquisition of equipment, and training of appropriate personnel.

Chondrosarcoma of the spine: 1954 to 1997.

OBJECT: Primary chondrosarcoma of the spine is extremely rare. During the last 43 years only 21 patients with this disease were registered at The University of Texas M. D. Anderson Cancer Center. The purpose of this study was to examine the demographic characteristics, treatments, and outcomes of this set of patients. METHODS: Medical records for 21 patients were reviewed. Age, sex, race, clinical presentation, tumor histology, tumor location in the spinal column, treatments, surgical details, and response to treatment were recorded. Surgical procedures were categorized as either gross-total resection or subtotal excision of tumor. Neurological function was assessed using Frankel's functional classification. Time to recurrence and survival analyses were performed using the Kaplan-Meier method. The median age of patients was 51 years, with fairly equal gender representation. Eighteen patients underwent at least one surgical procedure for a total of 28 surgical procedures: seven radical resections and 21 subtotal excisions. Radiation therapy was used in conjunction with 10 of the 28 surgical procedures. The median Kaplan-Meier estimate of overall survival for the entire group was 6 years (range 6 months-17 years). Tumors recurred after 18 of the 28 procedures. Kaplan-Meier analysis revealed a statistically significant difference in the per-procedure disease-free interval after gross-total resection relative to subtotal excision (exact log rank 3.39; p = 0.04). The addition of radiation therapy prolonged the median disease-free interval from 16 to 44 months, although this was not statistically significant (exact log rank 2.63; p = 0.16). CONCLUSIONS: Our results suggest that gross-total resection of the chondrosarcoma provides the best chance for prolonging the disease-free interval in patients. Subtotal excision should be avoided whenever possible. Addition of radiation therapy does not appear to lengthen significantly the disease-free interval in this patient population.

Combined chest wall resection with vertebrectomy and spinal reconstruction for the treatment of Pancoast tumors.

OBJECT: Traditionally, superior sulcus tumors of the lung that involve the chest wall and spinal column have been considered to be unresectable, and historically, patients harboring these tumors have been treated with local radiation therapy with, at best, modest results. The value of gross-total resection remains unclear in this patient population; however, with the recent advances in surgical technique and spinal instrumentation, procedures involving more radical removal of such tumors are now possible. At The University of Texas M. D. Anderson Cancer Center, the authors have developed a new technique for resecting superior sulcus tumors that invade the chest wall and spinal column. They present a technical description of this procedure and results in nine patients in whom stage IIIb superior sulcus tumors extensively invaded the vertebral column. METHODS: These patients underwent gross-total tumor resection via a combined approach that included posterolateral thoracotomy, apical lobectomy, chest wall resection, laminectomy, vertebrectomy, anterior spinal column reconstruction with methylmethacrylate, and placement of spinal instrumentation. There were six men and three women, with a mean age of 55 years (range 36-72 years). Histological examination revealed squamous cell carcinoma (three patients), adenocarcinoma (four patients), and large cell carcinoma (two patients). The mean postoperative follow-up period was 16 months. All patients are currently ambulatory or remained ambulatory until they died. Pain related to tumor invasion improved in four patients and remained unchanged in five. In three patients instrumentation failed and required revision. There was one case of cerebrospinal fluid leakage that was treated with lumbar drainage and one case of wound breakdown that required revision. Two patients experienced local tumor recurrence, and one patient developed a second primary lung tumor. CONCLUSIONS: The authors conclude that in selected patients, combined radical resection of superior sulcus tumors of the lung that involve the chest wall and spinal column may represent an acceptable treatment modality that can offer a potential cure while preserving neurological function and providing pain control.

Sacral chordoma: 40-year experience at a major cancer center.

OBJECTIVE: Sacral chordomas are relatively rare, locally invasive, malignant neoplasms. Despite surgical resection, adjuvant radiation therapy, and chemotherapy, recurrence is common. This study reviews our experience during the last 40 years at The University of Texas M.D. Anderson Cancer Center, to determine the effects of various treatment methods on the overall course of this disease process. METHODS: A retrospective study was performed. From 1954 to 1994, 27 patients with sacral chordomas were evaluated at our institution. RESULTS: There were 19 male and 8 female patients, with a mean age of 56 years (range, 27-80 yr). All except one of the patients presented with pain, and 17 of 27 showed evidence of autonomic dysfunction at initial presentation. Based on microscopic examination of surgical specimen margins, surgical procedures were categorized as either radical resection or subtotal excision. All patients underwent at least one surgical procedure, for a total of 67 procedures (28 radical resections and 39 subtotal excisions). Twelve patients underwent one operation, whereas nine underwent two procedures and six underwent more than two operations (range, 3-16 operations). Radiation therapy was used in conjunction with 13 of the 67 surgical procedures. The median Kaplan-Meier estimate of the overall survival time for the entire group was 7.38 years (range, 4 mo to 34 yr). Tumors recurred after 47 of the 67 procedures. The overall disease-free interval for patients undergoing radical resection was 2.27 years for each procedure, compared with 8 months for each procedure for patients treated with subtotal excision (log-rank test for the inequality between the two curves, 19.58; P<0.0001). The addition of radiation therapy prolonged the disease-free interval for patients undergoing subtotal resection (2.12 yr versus 8 mo; log-rank test for the inequality between the two curves, 5.82; P<0.02). CONCLUSION: Our results suggest frequent recurrences in the majority of patients with chordomas. Radical resection is associated with a significantly longer disease-free interval, compared with subtotal removal of the tumor. Addition of radiation after subtotal resection improves the disease-free interval, although radiation therapy can generally be used only once. Based on these findings, we think that, whenever possible, radical resection should be the treatment of choice for sacral chordomas.

Gastric cancer and metastasis to the brain.

BACKGROUND: Metastasis of gastric carcinoma to the brain is very uncommon. At The University of Texas M. D. Anderson Cancer Center (M. D. Anderson), less than 1% of patients with primary gastric carcinoma are found to have brain metastases. Little has been published regarding the evaluation and treatment of these patients. The purpose of this study was to review our experience with gastric cancer metastatic to the brain and to describe the efficacy of the treatment used. METHODS: Between 1957 and 1997, a total of 218,690 patients were seen for evaluation of malignant tumors at M. D. Anderson. Of these patients, 3320 (1.5%) had a diagnosis of gastric cancer; however, only 24 patients (0.7%) were found to have brain metastases on imaging studies or at autopsy. We performed a retrospective review of these 24 patients and divided them into three groups on the basis of the treatment they received. RESULTS: Group 1 included patients who received steroids alone (16 mg of dexamethasone, daily). Group 2 patients received 3000 cGy of whole-brain radiation therapy (WBRT) delivered in 10 fractions in addition to steroids. Group 3 patients were managed with surgical resection, WBRT, and steroids. There were 18 male and 6 female patients, with a median age of 53 years. The most common presenting symptoms were weakness, difficulty with balance, and headache. Of the 19 patients diagnosed antemortem, 11 patients developed neurological symptoms after the primary diagnosis of gastric carcinoma, whereas 8 patients developed neurological symptoms before the diagnosis of gastric cancer. Forty-five percent of patients had a single brain metastasis, whereas 55% had multiple lesions. All patients had systemic disease, with bone, liver, and lung involvement seen in 46%, 42%, and 29%, respectively. Nineteen of 24 patients received treatment after diagnosis of brain metastases. Four patients received steroids only (group 1), 11 patients received WBRT and steroids (group 2), and 4 patients were treated with surgery, WBRT, and steroids (group 3). Median survival was approximately 2 months for patients in groups 1 and 2, whereas group 3 patients had a median survival of slightly greater than I year. CONCLUSIONS: Our results suggest that the overall prognosis of patients with brain metastases from gastric cancer is extremely poor (median survival, 9 weeks). WBRT, as an adjuvant to steroid treatment, was not effective in improving outcome in our series. In selected patients, most of whom were relatively young and had less advanced systemic disease, surgical resection followed by WBRT was associated with relatively long survival times (median survival, 54 weeks).

Transthoracic vertebrectomy for metastatic spinal tumors.

OBJECT: Anterior approaches to the spine for the treatment of spinal tumors have gained acceptance; however, in most published reports, patients with primary, metastatic, or chest wall tumors involving cervical, thoracic, or lumbar regions of the spine are combined. The purpose of this study was to provide a clear perspective of results that can be expected in patients who undergo anterior vertebral body resection, reconstruction, and stabilization for spinal metastases that are limited to the thoracic region. METHODS: Outcome is presented for 72 patients with metastatic spinal tumors who were treated by transthoracic vertebrectomy at The University of Texas M. D. Anderson Cancer Center. The predominant primary tumors included renal cancer in 19 patients, breast cancer in 10, melanoma or sarcoma in 10, and lung cancer in nine patients. The most common presenting symptoms were back pain, which occurred in 90% of patients, and lower-extremity weakness, which occurred in 64% of patients. All patients underwent transthoracic vertebrectomy, decompression, reconstruction with methylmethacrylate, and anterior fixation with locking plate and screw constructs. Supplemental posterior instrumentation was required in seven patients with disease involving the cervicothoracic or thoracolumbar junction, which was causing severe kyphosis. After surgery, pain improved in 60 of 65 patients. This improvement was found to be statistically significant (p < 0.001) based on visual analog scales and narcotic analgesic medication use. Thirty-five of the 46 patients who presented with neurological dysfunction improved significantly (p < 0.001) following the procedure. Thirty-three patients had weakness but could ambulate preoperatively. Seventeen of these 33 regained normal strength, 15 patients continued to have weakness, and one patient was neurologically worse postoperatively. Of the 13 preoperatively nonambulatory patients, 10 could walk after surgery and three were still unable to walk but showed improved motor function. Twenty-one patients had complications ranging from minor atelectasis to pulmonary embolism. The 30-day mortality rate was 3%. The 1-year survival rate for the entire study population was 62%. CONCLUSIONS: These results suggest that transthoracic vertebrectomy and spinal stabilization can improve the quality of life considerably in cancer patients with spinal metastasis by restoring or preserving ambulation and by controlling intractable spinal pain with acceptable rates of morbidity and mortality.

Expression and localization of urokinase-type plasminogen activator in human spinal column tumors.

We have sought to determine the production and activity of serine proteases in primary and metastatic spinal tumors and the association of these enzymes with the invasive and metastatic properties of spinal column tumors. Using immunohistochemical techniques, the cellular localization and expression of urokinase-type plasminogen activator (uPA) was assessed, whereas its activity was determined by fibrin zymography, and the amounts of enzyme were measured by an enzyme-linked immunosorbent assay (ELISA) in primary spinal column tumors (chordoma, chondrosarcoma, and giant cell tumor) and metastatic tumors of the spine arising from various malignancies (breast, lung, thyroid, and renal cell carcinomas, and melanomas). Metastatic tumors displayed higher levels of uPA activity than did primary spinal tumors (P<0.001). Immunohistochemical analysis revealed that uPA expression was highest in metastases from lung and breast carcinomas and melanomas, followed by metastatic tumors from thyroid and renal cell carcinomas. Similar results were obtained for uPA activity and enzyme level as determined by fibrin zymography and ELISA, respectively. We conclude that metastatic spinal tumors possess higher levels of uPA expression and activity than the primary spinal tumors, which tend to be less aggressive and only locally invasive malignancies. The results suggest that the plasminogen system may participate in the metastasis of tumors to the spinal column.

Expression and role of matrix metalloproteinases MMP-2 and MMP-9 in human spinal column tumors.

Matrix metalloproteinases (MMPs) have been implicated in the process of tumor invasion and metastasis formation. Thus, we determined the expression of MMPs in various primary and metastatic spinal tumors in order to assess the role of these enzymes in spinal invasion. MMP expression was examined by immunohistochemical localization, and quantitative evaluation of MMP protein content was determined by enzyme-linked immunosorbant assay (ELISA) and Western blotting. MMP enzyme activity was determined by gelatin zymography. Lung carcinomas and melanomas metastatic to the spine were shown to have higher levels of MMP-9 activity than those of breast, thyroid, renal metastases and primary spinal tumors. Immunohistochemical analysis revealed similar difference in expression of MMP-9 in tissue samples. When the tissue samples were subjected to gelatin zymography for examination of MMP-2 and MMP-9 activity and to ELISA and Western blotting for quantitative estimation of protein content, the most striking results were obtained for lung carcinomas and melanomas relative to the other tumors. Lung carcinomas and melanomas metastatic to the spine had considerably higher levels of MMP-9 activity than those of primary spinal tumor or breast, thyroid, and renal carcinoma metastases. Within the metastatic tumor category, neoplasms that are known to be associated with the shortest overall survival rates and most aggressive behavior, such as lung carcinomas and melanomas, had the highest levels of MMP-2 and MMP-9 activity compared to those less aggressive metastatic tumors such as breast, renal cell, and thyroid carcinomas. Our results suggest that MMPs may contribute to the metastases to the spinal column, and overexpression of these enzymes may correlate with enhanced invasive properties of both primary and metastatic spinal tumors.

Pulmonary atelectasis and other respiratory complications after cardiopulmonary bypass and investigation of aetiological factors.

Radiological evidence of pulmonary complications and possible aetiological factors were investigated in 50 consecutive patients after heart operations with cardiopulmonary bypass. Atelectasis was the most frequent pulmonary complication except for small pleural effusions, with an incidence of 64 per cent. Several types of atelectasis frequently co-existed, with a predominance of the less extensive plate and subsegmental forms. The incidence of atelectasis was the same on each side and the site of atelectasis was basal in three quarters of the patients. Preoperative clinical and catheter data were unrelated to the incidence of atelectasis. There was a significant positive correlation between a short cardiopulmonary bypass time and plate atelectasis, between a large fluid load after bypass and segmental atelectasis, between re-operation for bleeding and subsegmental atelectasis and between post-operative gastric dilation and atelectasis. The type of operation, the use of the intra-aortic balloon and the length of postoperative respiratory ventilation were unrelated to the incidence of atelectasis. The mechanism of development of atelectasis is discussed.