Avian mud nest architecture by self-secreted saliva

Mud nests built by swallows (Hirundinidae) and phoebes (Sayornis) are stable granular piles attached to cliffs, walls, or ceilings. Although these birds have been observed to mix saliva with incohesive mud granules, how such biopolymer solutions provide the nest with sufficient strength to support the weight of the residents as well as its own remains elusive. Here, we elucidate the mechanism of strong granular cohesion by the viscoelastic paste of bird saliva through a combination of theoretical analysis and experimental measurements in both natural and artificial nests. Our mathematical model considering the mechanics of mud nest construction allows us to explain the biological observation that all mud-nesting bird species should be lightweight.

Bird nests come in a variety of forms made from diverse building materials (1, 2). Each type of bird nest is subjected to mechanical constraints imposed by material characteristics. To overcome these constraints, birds have devised brilliant architectural technologies, which provide inspiration for a novel materials processing scheme and help us to better understand animal behavior.For instance, some birds including storks (Cicioniidae) and eagles (Accipitidae) build nests by piling up hard filamentary materials such as twigs, harnessing their friction as the cohesion mechanism (3). Weaverbirds (Ploceidae) weave soft filamentary materials such as grass and fine leaves into a woven nest tied to a tree branch. Some bird species use their own saliva in nest building, which Darwin considered an example of natural selection (4). An extreme case is the Edible-nest Swiftlets, which build their nest purely of self-secreted saliva so that it can be attached to cliff walls and cave ceilings where the above twig piles and tied leaves are not allowed (5).Swallows (Hirundinidae), phoebes (Sayornis), and other mud nesters have developed a unique building material, a mixture of mud and their own saliva, in contrast to those made of purely collected or self-secreted materials (6) (Fig. 1). During construction, mud nesters repeatedly pile a beakful of wet mud on the nest, and liquid bridges are formed in the nest due to evaporation. While building a nest usually takes several weeks, a transition from wet to dry structures can occur within a few hours. Hence, the capillary forces of liquid bridges temporarily provide cohesion such as those in sandcastles. However, unlike sandcastles, dehydrated saliva comes into play for permanent cohesion after complete evaporation (SI Appendix, Supplementary Note 1).Open in a separate windowFig. 1.A nest of the barn swallow (H. rustica). (A) Photograph of a barn swallow nest, taken from under the ceiling of a house in Suwon-si, Gyunggi-do, South Korea (37°16′13.5″N 126°59′01.0″E). (B) SEM image of the nest surface. (C) Chemical composition analysis of the surface shown in B by EDS. The red area indicates a region containing mostly carbon atoms, which may originate from bird saliva. The green area indicates a region containing mostly the silicon atoms of clay particles.Mud itself cannot confer sufficient cohesion and adhesion in mud nests. The ability of mud nests to bear tensile loads originates from the gluing agent in the bird''s saliva, which permeates into granules as a liquid and binds them as a solid after solvent evaporation (6–8) (SI Appendix, Supplementary Note 2). The gluing agent is called mucin, a family of large glycoproteins that are ubiquitous in animal organs and form a mucus gel with versatile functionality (9). Fig. 1B shows the scanning electron microscopy (SEM) image of a barn swallow’s mud nest consisting of platelet clay particles and larger grains. Energy-dispersive spectroscopy (EDS) mapping image of Fig. 1C clearly shows regions corresponding to organic material which is presumed to be from bird’s saliva.Of particular interest and worth biophysical investigation are the tensile strength of the mud nest with hardened saliva, design principles associated with the saliva-originated strength, and the resulting effects on the evolution of these mud-nesting birds. Principles behind cohesion in granular materials, such as wet sands (10), cemented powder aggregates (11), construction materials (12), and pharmaceutical tablets (13), have been studied to date, exploring the stress transmission, elasticity, and failure (14–18), and the formation of solidified bridges (19–21). However, little attention has been paid to the cohesion effects of self-secreted polymer materials upon evaporation and the biologically constructed granular architecture like birds’ mud nests. Here we devised experimental techniques to measure the strength of the relatively small and fragile nest specimens in order to mechanically characterize birds’ mud nests. We elucidate how solutes from bird saliva generate solid bridges that give rise to macroscopic tensile strength, which has long awaited physicochemical explanation since its first observation (4). To characterize the design principle of bird''s mud nests, we investigated natural and three-dimensional (3D)-printed artificial nests with various tools for visualization and mechanical testing. Along with the experimental studies, we theoretically investigated the effects of biopolymer concentration on nest strength. This combination of theory and experiment suggests that there is a size limit for mud-nesting birds, which is supported by biological data.     

Utilization and Complications of Central Venous Access Devices in Oncology Patients

Purpose: To describe how central venous access devices (CVADs) are utilized for ambulatory oncology patients and to evaluate the rate of complications. Method: Single institution retrospective study of oncology patients with CVADs who received systemic treatment at the Walker Family Cancer Centre (WFCC) between 1 January and 31 December 2018. Results: A total of 480 CVADS were placed in 305 patients, of which 408 (85%) were peripherally inserted central catheters (PICCs) and 72 (15%) were implanted vascular access devices (PORTs). The incidence of early and late complications was 9% and 24%, respectively. For the entire cohort, the rate of venous thromboembolism (VTE) was 16%, of which 9% were CVAD-related thrombosis (CRTs) and 7% were distant VTE. The CRT rates were similar for PICCs and PORTs (9% vs. 7%). A total of 6% of CVADs were complicated by infection (i.e., localized infections and bacteremia), with a total infection rate of 0.43 and 0.26 per 1000 indwelling days for PICCs and PORTs, respectively. The incidence of central line associated bloodstream infections (CLABSI) was greater for PICCs than PORTs, at a rate of 0.22 compared with 0.08 per 1000 indwelling days, respectively. The premature catheter removal rate was 26% for PICCs and 18% for PORTs. PORTs required more additional hospital visits. Conclusions: PICCs were utilized more frequently than PORTs and had a higher rate of premature removal. The rates of VTE and CRT were similar for both CVAD types. PORTs had a lower rate of infection per 1000 indwelling days. However, the management of PORT related complications required more visits to the hospital and oncology clinic.     

Are clinical trial eligibility criteria representative of older patients with lung cancer? A population-based data linkage study

ObjectivesOlder adults constitute the majority of patients with lung cancer. However, they are under-represented in clinical trials as eligibility criteria often restrict enrolment based on comorbidities that are common with aging. We aimed to describe comorbidities relating to trial exclusion criteria in older adults with lung cancer, determine the proportion that would typically be excluded from trials, and examine the impact on treatment uptake.Materials and MethodsWe conducted a population-based study of people aged ≥65 years diagnosed with metastatic lung cancer using linked data for clients of the Australian Government Department of Veterans' Affairs (2005–2015). We defined trial-typical patients based on the absence of comorbidities related to the following: inadequate organ (cardiac, renal, hepatic, marrow) function; cognitive dysfunction; poor performance status (PS); prior malignancy within 5 years. We report systemic therapy uptake within 3 months of diagnosis.ResultsOur study included 677 patients (median age 84). Over half (53.4%) were not trial-typical, with the most common reasons being poor PS (37.5%), cardiac disease (19.2%), and prior cancer (12.9%). Eighty-two (12.1%) received systemic therapy. Patients with poor PS, cardiac disease, and dementia had lower treatment uptake rates. However, there was no significant difference in treatment uptake between trial-typical and non-trial-typical patients (13.4 vs 11.0%).ConclusionMore than half of older adults with advanced lung cancer would be typically excluded from trial participation. Future clinical trials of older adults need to consider broader eligibility criteria to better reflect this population to gain the best evidence for their care.     

Factors Associated with Reoperation in Breast-Conserving Surgery for Cancer: A Prospective Study of American Society of Breast Surgeon Members

Background

More than 20% of patients undergoing initial breast-conserving surgery (BCS) for cancer require reoperation. To address this concern, the American Society of Breast Surgeons (ASBrS) endorsed 10 processes of care (tools) in 2015 to be considered by surgeons to de-escalate reoperations. In a planned follow-up, we sought to determine which tools were associated with fewer reoperations.

Methods

A cohort of ASBrS member surgeons prospectively entered data into the ASBrS Mastery^® registry on consecutive patients undergoing BCS in 2017. The association between tools and reoperations was estimated via multivariate and hierarchical ranking analyses.

Results

Seventy-one surgeons reported reoperations in 486 (12.3%) of 3954 cases (mean 12.7% [standard deviation (SD) 7.7%], median 11.5% [range 0–32%]). There was an eightfold difference between surgeons in the 10th and 90th percentile performance groups. Actionable factors associated with fewer reoperations included routine planned cavity side-wall shaves, surgeon use of ultrasound (US), neoadjuvant chemotherapy, intra-operative pathologic margin assessment, and use of a pre-operative diagnostic imaging modality beyond conventional 2D mammography. For patients with invasive cancer, ≥ 24% of those who underwent reexcision did so for reported margins of < 1 or 2 mm, representing noncompliance with the SSO-ASTRO margin guideline.

Conclusions

Although ASBrS member surgeons had some of the lowest rates of reoperation reported in any registry, significant intersurgeon variability persisted. Further efforts to lower rates are therefore warranted. Opportunities to do so were identified by adopting those processes of care, including improved compliance with the SSO-ASTRO margin guideline, which were associated with fewer reoperations.

     

Sarcopenia with inflammation as a predictor of survival in patients with head and neck cancer

ObjectiveAlthough both sarcopenia and systemic inflammation affect the outcomes of head and neck cancer (HNC) patients, the association between sarcopenia and systemic inflammation and the combined prognostic effect of these factors in HNC patients remain unknown. This study aimed to evaluate the effect of sarcopenia with systemic inflammation on survival and disease control in HNC patients.MethodsWe retrospectively reviewed medical records of HNC patients treated between 2009 and 2016. The skeletal muscle area was measured using a single computed tomography image slice at the level of the third cervical vertebra. A prognostic score (SPLR) was developed based on sarcopenia and the platelet-lymphocyte ratio (PLR), and its prognostic value was evaluated.ResultsOverall, 164 patients were enrolled. In the multivariate analysis, sarcopenia was significantly associated with poor overall survival (OS) (p < 0.01). However, neither sarcopenia nor a high PLR was an independent prognostic factor for disease-free survival (DFS) or locoregional recurrence-free survival (LRFS). A high PLR was an independent predictor for sarcopenia (p < 0.01). A high SPLR was associated with older age, lower serum hemoglobin, and lower body mass index (all p < 0.05). Multivariate analysis revealed that SPLR was a significant independent predictor of OS, DFS, and LRFS (all p < 0.05).ConclusionsSystemic inflammation is significantly associated with sarcopenia. The survival and oncological effects of sarcopenia were enhanced when PLR was high. Thus, the combination of these two parameters may be useful for identifying HNC patients at a risk of poor survival outcomes.