Effect of regular swimming exercise to duration-intensity on neurocognitive function in cerebral infarction rat model

Objective: This study investigated the effect of regular swimming exercise according to the duration-intensity on neurocognitive function in a cerebral infarction rat model.

Methods: Forty male Sprague–Dawley 10-week-old rats, weighing 300 ± 50 g, were subjected to photothrombotic cerebral infarction. The remaining 36 rats were randomly divided into four groups (n = 9 per group: non-exercise (group A); swimming exercise of short duration-intensity (5 min/day, group B); swimming exercise of moderate duration-intensity (10 min/day, group C); and swimming exercise of long duration-intensity (20 min/day, group D). Exercise was performed five times a week for 4 weeks, beginning the day after cerebral infarction. Neurocognitive function was evaluated with the Morris water maze test. Immunohistochemistry and western blot analysis examined brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF) at 4 weeks postinfarction.

Results: At 4 weeks postinfarction, escape latency was found to be shorter in group C than in any of groups A, B, or D. Immunohistochemistry revealed the most significant immunoreactivity for BDNF and VEGF in group C. Western blot analysis demonstrated that BDNF and VEGF proteins were markedly expressed in group C.

Conclusions: Regular swimming exercise of moderate duration-intensity may be the most effective exercise protocol for the recovery of neurocognitive function in cerebral infarction rat model.     

Forearm wearable resistance effects on sprint kinematics and kinetics

Objectives

Arm swing is a distinctive characteristic of sprint-running with the arms working in a contralateral manner with the legs to propel the body in a horizontal direction. The purpose of this study was to determine the acute changes in kinematics and kinetics when wearable resistance (WR) of 1 kg (equivalent to ～1% body mass) was attached to each forearm during over ground short distance (20 m) maximal sprint-running.

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.     

Differences in the incidence of aflibercept-related sterile endophthalmitis according to types of disposable syringes used

Graefe's Archive for Clinical and Experimental Ophthalmology - To evaluate the difference between the incidences of sterile endophthalmitis after administration of intravitreal aflibercept...