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PubMed1999

Economic impact of hospital closure on small rural counties, 1984 to 1988: demonstration of a comparative analysis approach.

Hospital closure in a rural community may affect the locale's economic prospects as well as the health of its residents. Studies of economic effects have primarily relied on modeling techniques rather than observation of actual change. This study demonstrates the use of a comparative analysis approach for estimating the economic effects of hospital closure on small rural counties. The experiences of 103 small rural counties at which a hospital closed between 1984 and 1988 was compared with a matched group of counties at which no closure took place. "Comparable" counties were selected based on seven scales measuring the similarity between a closure county and potential comparisons. Three scales examined population and economic characteristics in the year before closure; two scales measured change throughout a three-year period preceding closure; and two scales measured change throughout a five-year period preceding closure. Closure effects were measured through a multivariate analysis of the post-closure economic history of closure and comparison counties. The key assumption is that similar counties should have similar experiences over time. If an event occurs within some of these counties but not others, this event should have visible effects. Comparative analysis suggested that earned income in closure counties (excluding farming and mining income) was lower than in comparison counties subsequent to closure and that labor force growth was similarly affected. A comparative analysis approach produces results that parallel those obtained from economic modeling and should be considered for further research.

Health Facility Closure↗
PubMed1992

Competing risks determining event-free survival in early breast cancer.

To evaluate the natural history of a disease and the effects of therapeutic interventions, it is important to determine which are the causes of treatment failure and to assess the extent to which each cause contributes to the total failure rate. The paper presents a new biostatistical technique to decompose the total event-free survival of a diseased population into cause-specific failure rates. The technique was based on a competing risk approach thereby avoiding biases related to assumptions of independence between different types of event. Such assumptions are inherent in the conventional Kaplan-Meier or actuarial methods. The competing risk method was used to analyse the pattern of failure among 2,850 pre- and postmenopausal patients with early-stage breast cancer and the results were compared to those obtained using conventional methods. The following events were analysed: loco-regional recurrence, distant metastasis, contralateral breast cancer, other new primary malignancies, and intercurrent deaths. The rate of new primary malignancies was found to be significantly higher in post- than in premenopausal patients (6% vs 3% at 10 years). In low-risk, node-negative postmenopausal patients the incidence of recurrences from breast cancer were found to be no greater than other types of events. This observation highlights the significance of the effect of different adjuvant therapies not only on the disease itself but also on the risk of second primary malignancies and other intercurrent diseases. In general, it was found that the conventional statistical methods tended to overestimate the event-specific rates. In conclusion, the method based on competing risks permits an unbiased analysis of all types of events determining the total event-free survival. It is thus useful for the description of the natural history of breast cancer as well as other diseases.

Aged↗
PubMed1990

Two-dimensional probability density analysis of single channel currents from reconstituted acetylcholine receptors and sodium channels.

Two-dimensional probability density analysis of single channel current recordings was applied to two purified channel proteins reconstituted in planar lipid bilayers: Torpedo acetylcholine receptors and voltage-sensitive sodium channels from rat brain. The information contained in the dynamic history of the gating process, i.e., the time sequence of opening and closing events was extracted from two-dimensional distributions of transitions between identifiable states. This approach allows one to identify kinetic models consistent with the observables. Gating of acetylcholine receptors expresses "memory" of the transition history: the receptor has two channel open (O) states; the residence time in each of them strongly depends on both the preceding open time and the intervening closed interval. Correspondingly, the residence time in the closed (C) states depends on both the preceding open time and the preceding closed time. This result confirms the scheme that considers, at least, two transition pathways between the open and closed states and extends the details of the model in that it defines that the short-lived open state is primarily entered from long-lived closed states while the long-lived open state is accessed mainly through short-lived closed states. Since ligand binding to the acetylcholine-binding sites is a reaction with channel closed states, we infer that the longest closed state (approximately 19 ms) is unliganded, the intermediate closed state (approximately 2 ms) is singly liganded and makes transitions to the short open state (approximately 0.5 ms) and the shortest closed state (approximately 0.4 ms) is doubly liganded and isomerizes to long open states (approximately 5 ms). This is the simplest interpretation consistent with available data. In contrast, sodium channels modified with batrachotoxin to eliminate inactivation show no correlation in the sequence of channel opening and closing events, i.e., have no memory of the transition history. This result is, therefore, consistent with any kinetic scheme that considers a single transition pathway between open and closed states, and confirms the C-C-O model previously inferred from one-dimensional distribution analysis. The strategy described should be of general validity in the analysis of single channel events from channel proteins in both natural and reconstituted membranes.

Animals↗
PubMed1994

Atherosclerosis of the ascending aorta. Prevalence and role as an independent predictor of cerebrovascular events in cardiac patients.

BACKGROUND AND PURPOSE: The cause of cerebral and peripheral embolism remains undetermined in a significant number of patients. An atherosclerotic thoracic aorta has thus far been considered to be an uncommon one. METHODS: To define the potential role of the ascending thoracic aorta as an embolic source, intraoperative ultrasonic aortic imaging was performed in 1200 of 1334 consecutive patients aged 50 years and older who were undergoing cardiac surgery. Patients were divided into two groups according to the results of the ultrasound study in terms of presence or absence of atherosclerotic disease. The prevalence of previous neurological events in the two groups was characterized and compared. RESULTS: Ascending aortic atherosclerosis was present in 231 (19.3%) of the patients studied. Patients in this category were older (P < .0001). A higher percentage of them were smokers (P < .0001) compared with patients with less severe disease. Coronary artery disease was more extensive (P = .012), and a higher percentage of these patients had a history of peripheral vascular disease (P < .0001). Univariate analysis of the subjects with (n = 158) and without (n = 1042) previous neurological events indicated that age, body mass index, atrial fibrillation, hypertension, and atherosclerosis of the ascending aorta were associated significantly with previous occurrence of a cerebrovascular accident. For the group as a whole, multiple logistic regression analysis demonstrated that hypertension (odds ratio, 1.81; P = .002), atherosclerosis of the ascending aorta (odds ratio, 1.65; P = .013), and atrial fibrillation (odds ratio, 1.54; P = .060) were significantly and independently associated with the occurrence of previous neurological events. CONCLUSIONS: Atherosclerosis of the ascending aorta is an independent risk factor for cerebrovascular events. An atherosclerotic ascending aorta may represent a potential source of emboli or may be a marker of generalized atherosclerosis.

Age Factors↗
PubMedDate not supplied

Lifelines: a life history methodology.

BACKGROUND: Life histories are data collection strategies that detail an individual's life Lifelines are a visual depiction of a life history, displaying events in chronological order and noting the importance, or meaning, of events. APPROACH: A sample lifeline from a study of young women's developmental transitions used to demonstrate the application of this technique to nursing research. A review life histories as well as lifeline techniques, analysis, and applications is included. DISCUSSION: Life history has been used extensively as a data collection method research, theory development, and clinical practice. The lifeline facilitates recollection and sequencing of personal events. The lifeline activity can be triangulated with other data collection methods such as interviews and focus groups to confirm and complete a life history or to place a particular research construct or clinical problem in the con text of other events.

Adaptation, Psychological↗
PubMed1998

Efficacy of ondansetron and prochlorperazine for the prevention of postoperative nausea and vomiting after total hip replacement or total knee replacement procedures: a randomized, double-blind, comparative trial.

BACKGROUND: Limited data are available on the efficacy of ondansetron hydrochloride compared with prochlorperazine maleate for the treatment of postoperative nausea and vomiting (PONV). OBJECTIVE: To evaluate the comparative efficacy of ondansetron and prochlorperazine for the prophylaxis of PONV in patients undergoing total hip replacement or total knee replacement procedures. METHODS: A randomized, double-blind, comparative trial was conducted at a tertiary care, university hospital. Seventy-eight patients undergoing elective total hip or total knee replacement procedures received a single dose of ondansetron hydrochloride (n = 37), 4 mg intravenously, or prochlorperazine maleate (n = 41), 10 mg intramuscularly, at the end of the surgical procedure. Rescue therapy was administered every 4 hours as needed during the initial 48 hours. Primary outcome measures were the incidences and severity of PONV. Secondary outcome measures included the number of rescue antiemetic doses required, number of physical therapy cancellations because of PONV, length of hospital stay, and cost of antiemetic agents administered. RESULTS: The incidence of nausea was significantly greater in the ondansetron group compared with the prochlorperazine group (81% vs 56%; odds ratio, 3.4; 95% confidence interval, 1.2-9.4) as was the severity of nausea (P = .04). Multivariate analysis identified administration of ondansetron, history of PONV, obesity, and female sex as risk factors for a nausea event. The incidence of vomiting tended to be greater in the ondansetron group (49% vs 32%; odds ratio, 2.0; 95% confidence interval, 0.8-5.0). The need for rescue antiemetic therapy was also greater in the ondansetron group (46% vs 27%; odds ratio, 2.3; 95% confidence interval, 0.9-6.0). The mean antiemetic drug cost per patient was significantly greater for the ondansetron group ($47.56 vs $2.47; P<.001). However, the proportion of patients who were unable to participate in physical therapy because of PONV and the median length of hospital stay were similar in both groups. CONCLUSION: Prochlorperazine is associated with superior efficacy and significant cost savings compared with ondansetron for the prevention of PONV in patients undergoing total hip and total knee replacement procedures.

Adult↗
PubMed1998

De novo mutations (GAG deletion) in the DYT1 gene in two non-Jewish patients with early-onset dystonia.

The DYT1 gene recently has been cloned and shown to contain a three nucleotide (GAG) deletion responsible for most cases of autosomal dominant early-onset torsion dystonia. This deletion results in the loss of one of a pair of glutamic acids in a conserved region of a novel ATP-binding protein (torsinA). Previous haplotype analysis revealed that this same deletion had arisen at least two different times in history, suggesting independent mutational events. This deletion is the only sequence change found thus far to be associated uniquely with the disease status, regardless of ethnic origin. Here we describe two patients with typical early-onset torsion dystonia of Swiss-Mennonite and non-Jewish Russian origin, respectively, that both carry this same mutation as a de novo GAG deletion. This finding proves that this 3 bp deletion in the DYT1 gene is indeed a mutation that causes early-onset torsion dystonia. The DYT1 mutation is one of the rare examples of the same recurrent mutation causing a dominantly inherited condition. The sequence surrounding the GAG deletion contains an imperfect 24 bp tandem repeat, suggesting a possible mechanism for the high frequency of this mutation.

Adult↗
PubMed1996

Tardive dyskinesia and pregnancy and delivery complications.

Twelve children and adolescents with movements suggestive of tardive dyskinesia (TD) were compared to 49 non-TD patients while receiving neuroleptic treatment. A multiple regression analysis revealed the diagnosis of TD to be significantly associated with a history of pregnancy and delivery complications (PDCs), suggesting that these events may increase the risk of the development of treatment emergent TD.

Adolescent↗
PubMed2000

Safety and prognostic value of early dobutamine-atropine stress echocardiography in patients with spontaneous chest pain and a non-diagnostic electrocardiogram.

AIMS: To risk stratify and shorten hospital stay in patients with spontaneous (resting) chest pain and a non-diagnostic electrocardiogram (ECG). METHODS AND RESULTS: The study comprised 102 patients (mean age 58+/-12 years, 67 men) with spontaneous chest pain and a non-diagnostic ECG. Forty-three patients had suspected coronary artery disease and 59 had known (but of unknown actual significance) coronary artery disease. All patients underwent serial creatine kinase enzyme measurements, continuous ECG monitoring for at least 12 h and early dobutamine-atropine stress echocardiography in patients with negative creatine kinase enzymes and normal findings at ECG monitoring. Dobutamine-atropine stress echocardiography was considered positive in patients with new or worsening wall thickening abnormalities. Patients with negative dobutamine-atropine stress echocardiography were discharged after the test. In-hospital and 6 month follow-up events noted were cardiac death, non-fatal myocardial infarction, unstable angina, and coronary artery bypass surgery or angioplasty. Thirteen patients had evidence of evolving myocardial infarction by elevated creatine kinase enzymes, or unstable angina by ECG monitoring. In the remaining 89 patients, dobutamine-atropine stress echocardiography was performed after a median observation period of 31 h (range 12-68 h). During dobutamine-atropine stress echocardiography no serious complications (death, non-fatal myocardial infarction, sustained ventricular tachycardia or ventricular fibrillation) occurred. Dobutamine-atropine stress echocardiography results were of poor quality in three, non-diagnostic in six, negative in 44 and positive in 36 patients. In the 80 patients with diagnostic dobutamine-atropine stress echocardiography, variables associated with in-hospital events (n=7) were history of exertional angina (P<0. 005), chest pain score (P<0.005), stress-induced angina (P<0.001) and positive dobutamine-atropine stress echocardiography (P<0.005). Variables associated with follow-up events (n=11) were history of exertional angina (P<0.05), chest pain score (P<0.001), stress-induced angina (P<0.01) and positive dobutamine-atropine stress echocardiography (P<0.01). At multivariate analysis the only significant predictor of events was positive dobutamine-atropine stress echocardiography (P<0.01). CONCLUSION: Early dobutamine-atropine stress echocardiography may safely distinguish between low- and high-risk subsets for subsequent cardiac events in patients with spontaneous chest pain and a non-diagnostic ECG.

Atropine↗
PubMedDate not supplied

Achalasia presenting after operative and nonoperative trauma.

Achalasia has been described following fundoplication and is attributed to vagal nerve damage during surgery. Similarly, other traumatic events to the distal esophagus may be linked to the development of achalasia. Operative and nonoperative trauma as a possible factor in the development of achalasia was studied. A retrospective analysis of patients with achalasia (n = 64) at our institution was performed. Collected data included age, gender, symptoms, and history of operative and nonoperative traumatic events. Comparisons were made to a group of patients with similar symptoms but normal esophageal manometry (n = 73). Achalasia was diagnosed by manometry in 125 patients over a 6-year period. All patients with complete medical records (n = 64) were studied. A history of operative or nonoperative trauma to the upper gastrointestinal tract prior to the development of symptomatic achalasia was present in 16 of 64 (25%). Significantly fewer patients (9.5%) with symptoms of dysphagia, but normal manometry and upper endoscopy, had precedent trauma to the upper gastrointestinal tract (P < 0.05). All cases of nonoperative trauma occurred in motor vehicle accidents. Cases of operative trauma included coronary artery bypass surgery (n = 4), bariatric surgery (n = 2), fundoplication (n = 3), heart/lung transplantation (n = 1), and others (n = 5). Patients with proven achalasia and a history of trauma were more likely to have chest pain (RR, 4.5; P = 0.012) but less likely to have regurgitation (RR, 0.51; P = 0.01) or nausea/vomiting (RR, 0.0; P = 0.27) than those without a history of antecedent trauma. In this series, significantly more patients with achalasia had a history of preceding trauma than did patients with similar symptoms and normal esophageal manometry. Following trauma, patients may be at increased risk for developing achalasia, possibly from neuropathic dysfunction due to vagal nerve damage. Patients with posttraumatic achalasia may have symptoms which differ from those of other achalasia patients.

Accidents, Traffic↗
PubMed2004

Psychological status at the menopausal transition: an Italian epidemiological study.

OBJECTIVES: To provide epidemiological data about psychological symptoms derived from a large Italian non-clinical sample, and to investigate the correlation with psychosocial factors. METHODS: The study design was a cross-sectional postal survey of a sample of menopausal women recruited from the General Registry Office in Ferrara's province. Four thousands and seventy-three women were sent a questionnaire designed on the basis of the Women Health Questionnaire (WHQ). Together with the WHQ, women were asked to fill out a personal file to define social status, cultural level, family's characteristics, recent menstrual cycles, gynaecological history and operations, drug's assumption, life events in the last year and lifetime depression. RESULTS: Factor analysis resulted in eight clusters of symptoms. Among psychiatric symptoms, three different clusters were identified: depressive symptoms, depressed mood with anxiety symptoms, and anxiety. The cluster "depressive symptoms" was more evident in the postmenopausal period with respect to the premenopausal one. CONCLUSION: The cluster "depressive symptoms" is significantly different in the premenopausal group with respect to the postmenopausal group, with greater levels of symptomatology in the postmenopausal group. On the contrary, the factor "depressed mood with anxiety symptoms" is present to the same extent in the pre-, peri- and postmenopausal groups. Prior depression is the most predictive variable of subsequent depression in postmenopausal women. Factors related to more pronounced depressive symptoms are number of life events, postmenopausal status, place of residence in rural areas and lower cultural level.

Cross-Sectional Studies↗
PubMed2006

Contribution of alcoholism to brain dysmorphology in HIV infection: effects on the ventricles and corpus callosum.

Nonrigid registration and atlas-based parcellation methods were used to compare the volume of the ventricular system and the cross-sectional area of the midsagittal corpus callosum on brain MRIs from 272 subjects in four groups: patients with HIV infection, with and without alcoholism comorbidity, alcoholics, and controls. Prior to testing group differences in regional brain metrics, each measure was corrected by regression analysis for significant correlations with supratentorial cranial volume and age, observed in 121 normal control men and women, whose age spanned six decades. Disregarding HIV disease severity, we observed a graded pattern of modest enlargement of the total ventricular system (0.28 SD for uncomplicated HIV, 0.65 SD for HIV comorbid with alcoholism, and 0.72 SD for the alcoholism group). The pattern of callosal thinning showed a similar but small ( approximately 0.5 SD) graded effect. A different pattern emerged, however, when HIV severity in the context of alcoholism comorbidity was factored into the analysis. Substantially greater volume abnormalities were present in individuals with a history of an AIDS-defining event or low CD4+ T cell counts (<or=200 mm(3)) irrespective of alcoholism comorbidity, and the effect of HIV severity was disproportionately exacerbated by alcoholism comorbidity, with 1 SD size deficit in the genu of corpus callosum and nearly 2 SD greater volume of the frontal and body regions of the ventricles for the AIDS + alcohol comorbid group. The differences in brain volumes between the AIDS groups with vs. without alcoholism could not be attributed to differences in HIV disease severity, defined by CD4+ count, viral load, or Karnofsky score. The substantial effect of the alcoholism-AIDS interaction on ventricular and callosal dysmorphology, in the context of the modest changes observed in non-AIDS, nonalcohol abusing HIV-infected individuals, highlight the need to consider alcohol use disorders as a major risk factor for neuropathology among HIV-infected persons.

Adult↗
PubMed1998

Slipping through sky holes: Yurok body imagery in northern California.

Yurok perceptions of the body as the inscribed surface of social and environmental change are explored in this paper. To the violence and brutality of Spaniards, fur traders, gold miners, American soldiers, and Indian policies of the US government since the eighteenth century, Yurok women attribute the high incidence of degenerative diseases, drug abuse and criminality in northern California. This piece contemplates the lives of eight generations of sixteen Yurok extended families, mapping intergenerational shifts in Yurok social relations and political practices. It considers the mutation of knowledge in the constitution of the natural and social sciences and the effects of this knowledge when implemented in Yurok country. Here, Foucault's genealogical method values what anthropology and biomedicine, for example, tend to disregard in the analysis of descent: the correlation between body and history. This historico-critical investigation shows how certain events mark their power and engrave memories on individuals' bodies. It is within a hybrid set of cross-cultural and interdisciplinary practices that a more fruitful understanding of Yurok body imagery can be fashioned.

Body Image↗
PubMed2003

The case of Dr. Shipman.

On January 31, 2000, Dr. Harold Shipman was convicted at Preston, England, of murdering 15 of his patients by administering lethal doses of diamorphine (pharmaceutical heroin). Investigations indicate that, during his working life, he killed about 220 to 240 of his patients. The bodies of many victims were cremated. Twelve victims were exhumed, and 9 of these deaths were included in the indictment. Most victims were elderly and had histories of natural disease. Autopsies confirmed known natural disease but showed no evidence of acute lethal events. Analysis of skeletal muscle disclosed significant quantities of morphine, to which the deaths were attributed. Circumstantial evidence was strong, as illustrated by the convictions in 6 deaths without autopsy or toxicology, because the bodies had been cremated. Organic compounds are remarkably stable in buried bodies. Even so, detection and quantitation of morphine in exhumed bodies may become problematic after burial for 4 years or more. Morphine glucuronide is slowly converted back to free morphine in the buried corpse.

Aged↗
PubMed2005

The effect of economic stability on family stability among welfare recipients.

The main rationale for defining two-parent families eligible for welfare was to keep families intact by eliminating an incentive for union dissolution. But there are other reasons for family instability, most notably women's reduced economic gain from marriage associated with having a chronically unemployed husband. This article explores the hypothesis that husband's unemployment increases union dissolution among welfare recipients. The analysis uses data from California's Link-Up demonstration project. A discrete-time event-history methodology was employed to examine family instability. The findings show that husband's unemployment and the family's long-term welfare dependency lead to breakup, net of race, age, and number of children.

California↗
PubMed2004

Association of house spraying with suppressed levels of drug resistance in Zimbabwe.

BACKGROUND: Public health strategies are needed to curb antimalarial drug resistance. Theoretical argument points to an association between malaria transmission and drug resistance although field evidence remains limited. Field observations, made in Zimbabwe, on the relationship between transmission and multigenic drug resistance, typified by chloroquine, are reported here. METHODS: Periodic assessments of the therapeutic response of uncomplicated falciparum malaria to chloroquine in two selectively sprayed or unsprayed health centre catchments, from 1995 - 2003. Cross-sectional analysis of in vivo chloroquine failure events for five sites in relation to natural endemicity and spraying history. RESULTS: During selective house spraying, the chloroquine failure rate for the sprayed catchment decreased, such that, after four years, the odds of chloroquine failure were 4x lower than before start of spraying in the area (OR 0.2, 95% CI 0.07 - 0.75, p = 0.010, n = 100). Chloroquine failure odds for the sprayed area became 4x lower than contemporaneous failure odds for the unsprayed area (OR 0.2 95% CI 0.08 - 0.65, p = 0.003, n = 156), although the likelihood of failure was not significantly different for the two catchments before selective spraying started (OR 0.5, 95% CI 0.21 - 1.32; p = 0.170, n = 88). When spraying ended, in 1999, the drug failure odds for the former sprayed area increased back 4 fold by 2003 (OR 4.2, 95%CI 1.49 - 11.78, p = 0.004, n = 146). High altitude areas with naturally lower transmission exhibited a 6x lower likelihood of drug failure than low-lying areas (OR 0.16 95% CI 0.068 - 0.353, -2 log likelihood change 23.239, p < 0.001, n = 465). Compared to sites under ongoing annual spraying, areas that were last sprayed 3-7 years ago experienced a 4-fold higher probability of chloroquine failure (OR 4.1, 95%CI 1.84 - 9.14, -2 log likelihood change 13.956, p < 0.001). CONCLUSION: Reduced transmission is associated with suppressed levels of resistance to chloroquine and presumably other regimens with multigenic drug resistance. It seems the adoption of transmission control alongside combination chemotherapy is a potent strategy for the future containment of drug-resistant malaria.

ATP-Binding Cassette Transporters↗
PubMed2006

Risk factors for growth of unruptured intracranial aneurysms: follow-up study by serial 0.5-T magnetic resonance angiography.

OBJECTIVE: The independent risk factors for aneurysm growth were retrospectively investigated in 130 patients with unruptured aneurysms who were followed up by 0.5-T serial magnetic resonance angiography with stereoscopic images. METHODS: Age, sex, site of aneurysm, size of aneurysm, multiplicity of aneurysms, type of circle of Willis, length of follow-up period, cerebrovascular event, hypertension, diabetes, hyperlipidemia, smoking habit, and family history of subarachnoid hemorrhage were investigated using multiple logistic analysis. RESULTS: Fourteen patients (16 aneurysms) among the 130 patients (159 aneurysms) showed aneurysm growth (10.8%) during follow-up of 10 to 69 months (mean 29.3 +/- 10.5 mo). Multiple logistic analysis disclosed that location on the middle cerebral artery (odds ratio [OR] 0.08, P < 0.01), multiplicity of aneurysms (OR 68.5, P < 0.01), aneurysm size of 5 mm or larger (OR 1.17, P = 0.05), and family history of subarachnoid hemorrhage (OR 10.9, P < 0.01) were independent risk factors. CONCLUSION: Location on the middle cerebral artery, multiplicity, aneurysm size of 5 mm or larger, and family history of subarachnoid hemorrhage are independent risk factors for aneurysm growth. These results may help to determine the treatment choice for unruptured aneurysms.

Aged↗
PubMed2000

Seabird and louse coevolution: complex histories revealed by 12S rRNA sequences and reconciliation analyses.

We investigated the coevolutionary history of seabirds (orders Procellariiformes and Sphenisciformes) and their lice (order Phthiraptera). Independent trees were produced for the seabirds (tree derived from 12S ribosomal RNA, isoenzyme, and behavioral data) and their lice (trees derived from 12S rRNA data). Brook's parsimony analysis (BPA) supported a general history of cospeciation (consistency index = 0.84, retention index = 0.81). We inferred that the homoplasy in the BPA was caused by one intrahost speciation, one potential host-switching, and eight or nine sorting events. Using reconciliation analysis, we quantified the cost of fitting the louse tree onto the seabird tree. The reconciled trees postulated one host-switching, nine cospeciation, three or four intrahost speciation, and 11 to 14 sorting events. The number of cospeciation events was significantly more than would be expected from chance alone (P < 0.01). The sequence data were used to test for rate heterogeneity for both seabirds and lice. Neither data set displayed significant rate heterogeneity. An examination of the codivergent nodes revealed that seabirds and lice have cospeciated synchronously and that lice have evolved at approximately 5.5 times the rate of seabirds. The degree of sequence divergence supported some of the postulated intrahost speciation events (e.g., Halipeurus predated the evolution of their present hosts). The sequence data also supported some of the postulated host-switching events. These results demonstrate the value of sequence data and reconciliation analyses in unraveling complex histories between hosts and their parasites.

Animals↗