The effects of heterospecific mating frequency on the strength of cryptic reproductive barriers.

Heterospecific mating frequency is critical to hybrid zone dynamics and can directly impact the strength of reproductive barriers and patterns of introgression. The effectiveness of post-mating prezygotic (PMPZ) reproductive barriers, which include reduced fecundity via heterospecific matings and conspecific sperm precedence, may depend on the number, identity and order of mates. Studies of PMPZ barriers suggest that they may be important in many systems, but whether these barriers are effective at realistic heterospecific mating frequencies has not been tested. Here, we evaluate the strength of cryptic reproductive isolation in two leaf beetles (Chrysochus auratus and C. cobaltinus) in the context of a range of heterospecific mating frequencies observed in natural populations. We found both species benefited from multiple matings, but the benefits were greater in C. cobaltinus and extended to heterospecific matings. We found that PMPZ barriers greatly limited hybrid production by C. auratus females with moderate heterospecific mating frequencies, but that their effectiveness diminished at higher heterospecific mating frequencies. In contrast, there was no evidence for PMPZ barriers in C. cobaltinus females at any heterospecific mating frequency. We show that integrating realistic estimates of cryptic isolation with information on relative abundance and heterospecific mating frequency in the field substantially improves our understanding of the strong directional bias in F1 production previously documented in the Chrysochus hybrid zone. Our results demonstrate that heterospecific mating frequency is critical to understanding the impact of cryptic post-copulatory barriers on hybrid zone structure and dynamics, and that future studies of such barriers should incorporate field-relevant heterospecific mating frequencies.

Cryptic gametic interactions confer both conspecific and heterospecific advantages in the Chrysochus (Coleoptera: Chrysomelidae) hybrid zone.

Most species pairs are isolated through the collective action of a suite of barriers. Recent work has shown that cryptic barriers such as conspecific sperm precedence can be quite strong, suggesting that they evolve quickly. However, because the strength of multiple barriers has been formally quantified in very few systems, the relative speed with which conspecific sperm precedence evolves remains unclear. Here, we measure the strength of both conspecific sperm precedence and cryptic non-competitive isolation between the hybridizing sister species, Chrysochus auratus and C. cobaltinus (Coleoptera: Chrysomelidae), and compare the strength of those barriers to the strength of other known reproductive barriers in this system. Overall, cryptic barriers in this system are weaker than other barriers, indicating that they have not evolved rapidly. Furthermore, their evolution has been asymmetric. Non-competitive barriers substantially reduce the production of hybrid offspring by C. auratus females but not by C. cobaltinus females. In multiply-mated C. cobaltinus females, heterospecific sperm outcompete conspecific sperm, as evidenced by the fact that heterospecific males sired disproportionately more offspring than predicted from the results for singly-mated females. In C. auratus females, neither sperm type has a competitive advantage. Such asymmetries explain why nearly all F1 hybrids in the field are from crosses between C. cobaltinus females and C. auratus males. We discuss these findings in terms of understanding the cost of mating 'mistakes' in the Chrysochus hybrid zone. In addition, our discovery that 95% confidence intervals for commonly-used isolation statistics can be very wide has important implications for speciation research. Specifically, to avoid biases in the interpretation of such isolation metrics, we suggest that studies should routinely include error estimates in their analyses of reproductive isolation.

Superiorly-based turnover skin flap: Pediatric tracheocutaneous fistula closure.

OBJECTIVE: To present a novel superiorly-based turnover skin flap for the primary repair of pediatric tracheocutaneous fistula closure, and to determine the efficacy and safety of this tracheocutaneous fistula turnover flap primary closure technique. SUBJECT AND METHODS: This retrospective review analyzed one surgeon's (DJK) pediatric tracheostomy decannulation methods and results, specifically relating to the development of tracheocutaneous fistulas, over a fourteen-year period, from October 2002 through June 2016. The review furthermore examined a turnover flap technique for the primary closure of tracheocutaneous fistulas described herein. RESULTS: Over the period of study, 57 patients were decannulated, of whom 31 (54%) developed a tracheocutaneous fistula. Mean duration of tracheostomy in patients who developed a tracheocutaneous fistula following decannulation was forty-two months compared to thirteen months in patients who did not. Duration of decannulation was an independently significant variable (P < .001) in tracheocutaneous fistula development while gender, age at tracheostomy and age at decannulation were not (P > .05). Of the 31 patients who developed a tracheocutaneous fistula, 30 (97%) elected to pursue tracheocutaneous fistula closure using the turnover flap technique described in this study. Mean time from decannulation to tracheocutaneous fistula repair was 132 days. All tracheocutaneous fistulas were successfully closed. There were no perioperative or postoperative complications and no patient required subsequent hospitalization or surgical revision. CONCLUSIONS: The turnover technique presented is simple, straightforward, reliable, safe, and effective with excellent cosmetic results.

Considerations for the successful decannulation of the pediatric patient: A single surgeon's experience.

OBJECTIVE: To characterize the steps and interventions necessary for successful decannulation of the chronic pediatric tracheostomy patient. METHODS: This retrospective review analyzed one surgeon's (DJK) pediatric tracheostomy decannulation methods and results at a tertiary academic medical center over a thirteen-year period, from October 2002 through November 2015. It also examined which tests and procedures were conducted on patients prior to their successful decannulation. RESULTS: Over the period of study, 46 patients met inclusion criteria for analysis and underwent decannulation after being followed in the clinic or the hospital. One of these patients had to have the tracheostomy tube replaced. In nearly all cases, these patients underwent a systematic progression from tolerance of daytime tracheostomy capping to a capped sleep study, and endoscopic airway evaluation. In recent years, a subset of patients also underwent sleep endoscopy. In nearly all cases, patients spent a single night in the hospital in a non-acute bed at the time of decannulation. Ninety-eight percent (n = 45) of patients were successfully and safely decannulated after having met the milestones that we employ at our institution. CONCLUSIONS: This study serves as a safe, efficient, and resource-prudent protocol for otolaryngologists to follow when considering tracheostomy decannulation in the pediatric population. Sleep endoscopy can play a helpful role in guiding decannulation decisions. Since it is impossible to employ a single rigid protocol of testing prior to decannulating all patients, clinical judgment must always be exercised in individual circumstances.

High resolution T2 MRI in the diagnosis of cerebellopontine angle and internal auditory canal lesions.

High resolution T2 magnetic resonance imaging (MRI) can provide exquisite detail of internal auditory canal (IAC) and cerebellopontine angle (CPA) lesions. In this retrospective case series, blinded imaging sequences were delivered to three radiologists and compared with previously archived clinical reads that were non-blinded and incorporated both T1+C and T2 sequences together. This article demonstrates high sensitivity and specificity for high resolution T2 MRI particularly with lesions >5mm. This suggests a role for high resolution T2 MRI as an initial screening sequence or as a surveillance sequence.

What is asthma? Pathophysiology, demographics, and health care costs.

Asthma is an obstructive pulmonary disorder with exacerbations characterized by symptoms of shortness of breath, cough, chest tightness, and/or wheezing. Symptoms are caused by chronic airway inflammation. There are multiple cell types and inflammatory mediators involved in its pathophysiology. The airway inflammation is frequently mediated by Th2 lymphocytes, whose cytokine secretion leads to mast cell stimulation, eosinophilia, leukocytosis, and enhanced B-cell IgE production. Although various genes have been identified as likely contributors to asthma development, asthma is largely environmentally triggered and has a multifactorial cause. Asthma is extremely common, especially in poor, urban environments. Asthma is the third most common reason for pediatric hospitalizations.

Maximum phonation time in healthy older adults.

OBJECTIVES/HYPOTHESIS: Maximum phonation time (MPT), a clinical measurement of the longest time one can phonate a vowel, typically /a/, is a frequently used measure of vocal function, but normative data are lacking for MPT in healthy older adults. The aim of this study was to provide data on MPT in healthy older adults and to determine the effect of advanced age, gender, and repeated measures on MPT. STUDY DESIGN: Prospective. METHODS: Sixty-nine healthy older adult volunteers participated (ie, 15, 26, and 28 in the seventh, eighth, and ninth decades of life, respectively). The effects of age, gender, and repeated measures (three trials in a single session) on MPT were assessed. Mean, standard deviation, compound symmetry covariance, analysis of variance, and analysis of covariance were used for statistical analysis. RESULTS: Neither age group, gender, trial, nor their interactions was statistically significant (P>0.05). Adults in the seventh, eighth, and ninth decades of life had mean MPTs of 22.27 (standard error [SE]=1.56), 22.97 (SE=1.11), and 21.14 (SE=0.97) seconds, respectively. Females and males had mean MPTs of 20.96 (SE=0.92) and 23.23 (SE=0.96) seconds, respectively. Finally, MPTs for trials 1, 2, and 3 were 21.77 (SE=1.09), 21.67 (SE=1.12), and 22.80 (SE=1.27), respectively. CONCLUSIONS: MPTs were longer in this group of older adults than previously reported and did not vary significantly with age or gender. Additionally, across a single short sampling session, measurements were relatively stable across three trials of MPTs.

Factors influencing bolus dwell times in healthy older adults assessed endoscopically.

OBJECTIVES/HYPOTHESIS: Scant data exist on normal bolus dwell time assessed during flexible endoscopic evaluation of swallowing (FEES). The purpose of this study was to examine bolus dwell time in healthy older adults. Because it has been previously reported that some healthy older adults aspirate, we also sought to determine if bolus dwell time varied as a function of aspiration status. STUDY DESIGN: Prospective. METHODS: Seventy-six healthy volunteers from the seventh, eighth, and ninth decades of life participated. Dwell times were analyzed via FEES as a function of pharyngeal location, liquid type, delivery method, purée type, viscosity, age, and gender. RESULTS: Longer dwell times were evidenced with the eldest participants, straw delivery, and the smallest volume. Adults in the ninth decade were 4.8 (P = .01) and 3.8 (P = .02) times more likely to have longer dwell times at the vallecula and 7.1 (P = .002) and 3.8 (P = 0.02) at the pyriform sinus than those in the seventh and eighth decades, respectively. Longer dwell times at the vallecula and pyriform sinuses were 2 and 2.38 times (P < .0001) more likely for straw than cup delivery, respectively. Boluses of 5 mL were 1.5 times (P < .05) more likely to result in longer dwell times than larger volumes. Bolus dwell times did not significantly differ as a function of aspiration status. CONCLUSIONS: Advanced age, straw delivery, and small volumes yielded longer dwell times. These variables should be considered before diagnosing an abnormal bolus dwell time in elder patients.