YYY Dynamic Tuning of Viscoelastic Hydrogels with Carbonyl Iron Microparticles Reveals the Rapid Response of Cells to Three-Dimensional Substrate Mechanics

Current methods to dynamically tune three-dimensional hydrogel mechanics require specific chemistries and substrates that make modest, slow, and often irreversible changes in their mechanical properties, exclude the use of protein-based scaffolds, or alter the hydrogel microstructure and pore size. Here, we rapidly and reversibly alter the mechanical properties of hydrogels consisting of extracellular matrix proteins and proteoglycans by adding carbonyl iron microparticles (MPs) and applying external magnetic fields. This approach drastically alters hydrogel mechanics: rheology reveals that application of a 4000 Oe magnetic field to a 5 mg/mL collagen hydrogel containing 10 wt % MPs increases the storage modulus from approximately 1.5 to 30 kPa. Cell morphology experiments show that cells embedded within these hydrogels rapidly sense the magnetically induced changes in ECM stiffness. Ca2+ transients are altered within seconds of stiffening or subsequent softening, and slower but still dynamic changes occur in YAP nuclear translocation in response to time-dependent application of a magnetic field. The near instantaneous change in hydrogel mechanics provides new insight into the effect of changing extracellular stiffness on both acute and chronic changes in diverse cell types embedded in protein-based scaffolds. Due to its flexibility, this method is broadly applicable to future studies interrogating cell mechanotransduction in three-dimensional substrates

Pitch then power: limitations to acceleration in quadrupeds

Rapid acceleration and deceleration are vital for survival in many predator and prey animals and are important attributes of animal and human athletes. Adaptations for acceleration and deceleration are therefore likely to experience strong selective pressures—both natural and artificial. Here, we explore the mechanical and physiological constraints to acceleration. We examined two elite athletes bred and trained for acceleration performance (polo ponies and racing greyhounds), when performing maximal acceleration (and deceleration for ponies) in a competitive setting. We show that maximum acceleration and deceleration ability may be accounted for by two simple limits, one mechanical and one physiological. At low speed, acceleration and deceleration may be limited by the geometric constraints of avoiding net nose-up or tail-up pitching, respectively. At higher speeds, muscle power appears to limit acceleration

Resilin and chitinous cuticle form a composite structure for energy storage in jumping by froghopper insects

RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are.Abstract Background Many insects jump by storing and releasing energy in elastic structures within their bodies. This allows them to release large amounts of energy in a very short time to jump at very high speeds. The fastest of the insect jumpers, the froghopper, uses a catapult-like elastic mechanism to achieve their jumping prowess in which energy, generated by the slow contraction of muscles, is released suddenly to power rapid and synchronous movements of the hind legs. How is this energy stored? Results The hind coxae of the froghopper are linked to the hinges of the ipsilateral hind wings by pleural arches, complex bow-shaped internal skeletal structures. They are built of chitinous cuticle and the rubber-like protein, resilin, which fluoresces bright blue when illuminated with ultra-violet light. The ventral and posterior end of this fluorescent region forms the thoracic part of the pivot with a hind coxa. No other structures in the thorax or hind legs show this blue fluorescence and it is not found in larvae which do not jump. Stimulating one trochanteral depressor muscle in a pattern that simulates its normal action, results in a distortion and forward movement of the posterior part of a pleural arch by 40 μm, but in natural jumping, the movement is at least 100 μm. Conclusion Calculations showed that the resilin itself could only store 1% to 2% of the energy required for jumping. The stiffer cuticular parts of the pleural arches could, however, easily meet all the energy storage needs. The composite structure therefore, combines the stiffness of the chitinous cuticle with the elasticity of resilin. Muscle contractions bend the chitinous cuticle with little deformation and therefore, store the energy needed for jumping, while the resilin rapidly returns its stored energy and thus restores the body to its original shape after a jump and allows repeated jumping

The effects of temperature and body mass on jump performance of the locust Locusta migratoria

Locusts jump by rapidly releasing energy from cuticular springs built into the hind femur that deform when the femur muscle contracts. This study is the first to examine the effect of temperature on jump energy at each life stage of any orthopteran. Ballistics and high-speed cinematography were used to quantify the energy, distance, and take-off angle of the jump at 15, 25, and 35°C in the locust Locusta migratoria. Allometric analysis across the five juvenile stages at 35°C reveals that jump distance (D; m) scales with body mass (M; g) according to the power equation D = 0.35M0.17±0.08 (95% CI), jump take-off angle (A; degrees) scales as A = 52.5M0.00±0.06, and jump energy (E; mJ per jump) scales as E = 1.91M1.14±0.09. Temperature has no significant effect on the exponent of these relationships, and only a modest effect on the elevation, with an overall Q10 of 1.08 for jump distance and 1.09 for jump energy. On average, adults jump 87% farther and with 74% more energy than predicted based on juvenile scaling data. The positive allometric scaling of jump distance and jump energy across the juvenile life stages is likely facilitated by the concomitant relative increase in the total length (Lf+t; mm) of the femur and tibia of the hind leg, Lf+t = 34.9M0.37±0.02. The weak temperature-dependence of jump performance can be traced to the maximum tension of the hind femur muscle and the energy storage capacity of the femur's cuticular springs. The disproportionately greater jump energy and jump distance of adults is associated with relatively longer (12%) legs and a relatively larger (11%) femur muscle cross-sectional area, which could allow more strain loading into the femur's cuticular springs. Augmented jump performance in volant adult locusts achieves the take-off velocity required to initiate flight.Edward P. Snelling, Christie L. Becker, Roger S. Seymou

Antibody Labelling of Resilin in Energy Stores for Jumping in Plant Sucking Insects

The rubbery protein resilin appears to form an integral part of the energy storage structures that enable many insects to jump by using a catapult mechanism. In plant sucking bugs that jump (Hemiptera, Auchenorrhyncha), the energy generated by the slow contractions of huge thoracic jumping muscles is stored by bending composite bow-shaped parts of the internal thoracic skeleton. Sudden recoil of these bows powers the rapid and simultaneous movements of both hind legs that in turn propel a jump. Until now, identification of resilin at these storage sites has depended exclusively upon characteristics that may not be specific: its fluorescence when illuminated with specific wavelengths of ultraviolet (UV) light and extinction of that fluorescence at low pH. To consolidate identification we have labelled the cuticular structures involved with an antibody raised against a product of the Drosophila CG15920 gene. This encodes pro-resilin, the first exon of which was expressed in E. coli and used to raise the antibody. We show that in frozen sections from two species, the antibody labels precisely those parts of the metathoracic energy stores that fluoresce under UV illumination. The presence of resilin in these insects is thus now further supported by a molecular criterion that is immunohistochemically specific

Toksični učinci olova u profesionalno izložene indijske obitelji

This article describes an entire family manufacturing lead acid batteries who all suffered from lead poisoning. The family of five lived in a house, part of which had been used for various stages of battery production for 14 years. Open space was used for drying batteries. They all drank water from a well located on the premises. Evaluation of biomarkers of lead exposure and/or effect revealed alarming blood lead levels [(3.92±0.94) µmol L-1], 50 % reduction in the activity of δ-aminolevulinic acid dehydratase [(24.67±5.12) U L-1] and an increase in zinc protoporphyrin [(1228±480) µg L-1]. Liver function tests showed an increase in serum alkaline phosphatase [(170.41±41.82) U L-1]. All other liver function test parameters were normal. Renal function tests showed an increase in serum uric acid [(515.81±86.29) µmol L-1] while urea and creatinine were normal. Serum calcium was low [(1.90±0.42) mmol L-1 in women and (2.09±0.12) mmol L-1 in men], while blood pressure was high in the head of the family and his wife and normal in children. Lead concentration in well water was estimated to 180 µg L-1. The family was referred to the National Referral Centre for Lead Poisoning in India, were they were received treatment and were informed about the hazards of lead poisoning. A follow up three months later showed a slight decrease in blood lead levels and a significant increase in haemoglobin. These findings can be attributed to behavioural changes adopted by the family, even though they continued producing lead batteries.Olovo je sveprisutni metal s mnogo namjena, a čovječanstvo ga rabi već više od 6000 godina. Danas je olovo među najrasprostranjenijim toksinima u okolišu, a drugi je na popisu toksičnih metala, odmah iza arsena. Mnogi još nisu svjesni njegova toksičnoga djelovanja te se i dalje izlažu olovu. Ovdje je opisana obitelj koja proizvodi olovne akumulatore i koja je pretrpjela trovanje olovom zahvaljujući svojoj neobaviještenosti. Ova peteročlana obitelj živjela je u jednome kućanstvu čiji je dio namijenjen različitim fazama proizvodnje akumulatora već 14 godina. Akumulatori su se sušili na otvorenome. Na imanju je bio i bunar s pitkom vodom. Mjerenja biopokazatelja izloženosti olovu i njegova djelovanja u svih pet članova obitelji dovela su do alarmantnoga saznanja o razinama olova u krvi [(3,92±0,94) µmol L-1], 50 %-tnom padu aktivnosti dehidrataze δ-aminolevulinske kiseline [(24,67±5,12) U L-1] te povišenom cinkovu protoporfirinu [(1228±480) µg L-1]. Jetrene probe otkrile su povišene razine alkalne fosfataze u serumu [(170,41±41,82) U L-1]. Ostali su parametri jetrene funkcije bili normalni. Testovi funkcije bubrega otkrili su povišene razine mokraćne kiseline u serumu [(515,81±86,29) µmol L-1], dok su razine ureje i kreatinina bile normalne. Također je zabilježen pad razina kalcija u serumu [(1,90±0,42) mmol L-1 u žena te (2,09±0,12) mmol L-1 u muškaraca]. Povišeni krvni tlak zamijećen je u glave obitelji i njegove supruge, dok je u djece bio normalan. Koncentracija olova u bunarskoj vodi bila je izrazito visoka, prema procjeni 180 µg L-1. Obitelj je upućena u indijski Državni referalni centar za otrovanje olovom (National Referral Centre for Lead Poisoning) gdje je primila lijekove i bila upoznata s činjenicama vezanim uz otrovanje olovom. Tromjesečno je praćenje pokazalo blagi pad razina olova u krvi te značajan porast hemoglobina. Ovi se nalazi mogu pripisati promjenama u ponašanju obitelji, bez obzira na to što je nastavila proizvoditi akumulatore

A RCT of a Transdiagnostic Internet-Delivered Treatment for Three Anxiety Disorders: Examination of Support Roles and Disorder-Specific Outcomes

BACKGROUND: Anxiety disorders share common vulnerabilities and symptoms. Disorder-specific treatment is efficacious, but few access evidence-based care. Administering transdiagnostic cognitive-behavioral therapy via the internet (iCBT) may increase access to evidence-based treatment, with a recent randomized controlled trial (RCT) providing preliminary support for this approach. This study extends those findings and aims to answer three questions: Is a transdiagnostic iCBT program for anxiety disorders efficacious and acceptable? Does it result in change for specific disorders? Can good clinical outcomes be obtained when guidance is provided via a Coach rather than a Clinician? METHOD: RCT (N = 131) comparing three groups: Clinician-supported (CL) vs. Coach-supported (CO) vs. waitlist control (Control). Individuals met DSM-IV criteria for a principal diagnosis of generalized anxiety disorder (GAD), social phobia (SP) or panic disorder with or without agoraphobia (Pan/Ag). Treatment consisted of an 8-lesson/10 week iCBT program with weekly contact from a Clinician or Coach, and follow-up at 3-months post-treatment. RESULTS: Outcomes for the pooled treatment groups (CL+CO) were superior to the Control group on measures of anxiety, depression and disability, were associated with medium to large effect sizes (Cohen's d = .76-1.44) (response rate = 89-100%), and were maintained at follow-up. Significant reductions were found on disorder-specific outcomes for each of the target diagnoses, and were associated with large effect sizes. CO participants achieved similar outcomes to CL participants at post-treatment, yet had significantly lower symptom severity scores on general anxiety, panic-disorder, depression and disability at follow-up (d = .45-.46). Seventy-four percent of CO and 76% of CL participants completed the program. Less than 70 minutes of Clinician or Coach time was required per participant during the program. DISCUSSION: This transdiagnostic iCBT course for anxiety appears to be efficacious, associated with significant change for three target disorders, and is efficacious when guided by either a Clinician or Coach. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry ACTRN12610000242022

Tools for crushing diatoms – opal teeth in copepods feature a rubber-like bearing composed of resilin

Diatoms are generally known for superior mechanical properties of their mineralised shells. Nevertheless, many copepod crustaceans are able to crush such shells using their mandibles. This ability very likely requires feeding tools with specific material compositions and properties. For mandibles of several copepod species silica-containing parts called opal teeth have been described. The present study reveals the existence of complex composite structures, which contain, in addition to silica, the soft and elastic protein resilin and form opal teeth with a rubber-like bearing in the mandibles of the copepod Centropages hamatus. These composite structures likely increase the efficiency of the opal teeth while simultaneously reducing the risk of mechanical damage. They are supposed to have coevolved with the diatom shells in the evolutionary arms race, and their development might have been the basis for the dominance of the copepods within today's marine zooplankton

Characterization and Generation of Male Courtship Song in Cotesia congregata (Hymenoptera: Braconidae)

Background Male parasitic wasps attract females with a courtship song produced by rapid wing fanning. Songs have been described for several parasitic wasp species; however, beyond association with wing fanning, the mechanism of sound generation has not been examined. We characterized the male courtship song of Cotesia congregata (Hymenoptera: Braconidae) and investigated the biomechanics of sound production. Methods and Principal Findings Courtship songs were recorded using high-speed videography (2,000 fps) and audio recordings. The song consists of a long duration amplitude-modulated “buzz” followed by a series of pulsatile higher amplitude “boings,” each decaying into a terminal buzz followed by a short inter-boing pause while wings are stationary. Boings have higher amplitude and lower frequency than buzz components. The lower frequency of the boing sound is due to greater wing displacement. The power spectrum is a harmonic series dominated by wing repetition rate ~220 Hz, but the sound waveform indicates a higher frequency resonance ~5 kHz. Sound is not generated by the wings contacting each other, the substrate, or the abdomen. The abdomen is elevated during the first several wing cycles of the boing, but its position is unrelated to sound amplitude. Unlike most sounds generated by volume velocity, the boing is generated at the termination of the wing down stroke when displacement is maximal and wing velocity is zero. Calculation indicates a low Reynolds number of ~1000. Conclusions and Significance Acoustic pressure is proportional to velocity for typical sound sources. Our finding that the boing sound was generated at maximal wing displacement coincident with cessation of wing motion indicates that it is caused by acceleration of the wing tips, consistent with a dipole source. The low Reynolds number requires a high wing flap rate for flight and predisposes wings of small insects for sound production