This study was designed to determine the regional differences of magnetic resonance (MR) measurements in the hamstrings [biceps femoris muscle long head (BFl) and short head (BFs), semimembranosus muscle (SM), and semitendinosus muscle (ST)] following eccentric knee-flexion exercise. Twelve male volunteers performed eccentric knee-flexion exercise. Maximum isometric torque, plasma creatine kinase (CK) activity, muscle soreness, and MR images of the hamstrings were measured before and immediately following exercise, and on the first, second, third and seventh days following the exercise. Cross-sectional areas (CSAs) and transverse relaxation times (T2s) of the hamstrings were measured from the T2-weightened MR imaging sequences of 30% (proximal), 50% (middle), and 70% (distal) areas of the thigh length. The CSA of the ST at proximal and middle regions had significantly increased on the third day, but no significant changes were found for the BFl or SM. Immediately following exercise, T2 values had increased significantly in the BFs, BFl, and ST. On the third day, T2 values of only ST increased significantly at proximal, middle and distal regions. Significant differences of T2 values between proximal and distal regions in the ST were found for the second, third and seventh days following the exercise. These results suggest that because of the anatomical characteristics of the muscles, the degrees of response following the exercise differed among the muscles and the regions of ST muscle.
Juvenile songbirds learn vocal communication from adult tutors of the same species but not from adults of other species. How species-specific learning emerges from the basic features of song prosody remains unknown. In the zebra finch auditory cortex, we discovered a class of neurons that register the silent temporal gaps between song syllables and are distinct from neurons encoding syllable morphology. Behavioral learning and neuronal coding of temporal gap structure resisted song tutoring from other species: Zebra finches fostered by Bengalese finch parents learned Bengalese finch song morphology transposed onto zebra finch temporal gaps. During the vocal learning period, temporal gap neurons fired selectively to zebra finch song. The innate temporal coding of intersyllable silent gaps suggests a neuronal barcode for conspecific vocal learning and social communication in acoustically diverse environments.
The fatigue properties of the soluted and the sensitized type 304 stainless steel were investigated in high pressure hydrogen up to 4.0 MPa at room temperature. It is found that both the number of cycles to failure and the fatigue limits of the soluted and the sensitized steel decreased with increasing hydrogen pressure. Typical fatigue fracture modes were observed on a main fatigue crack growth area of the fracture surface, that is, the striations in argon and the transgranular fracture in hydrogen, respectively. It is concluded that the fatigue crack growth is promoted by hydrogen along the boundary surface between the martensite and the austenite. The material tested was the type 304 stainless steel. It was solution annealed at 1373 K for 3.6ks, water quenched and used as a soluted specimen. It was further sensitized at 973 K 360ks and used as a sensitized one. These specimens were machined to a shape with a continuous by changing radius between both ends, as shown in Fig. 1, and annealed in vacuum at 573K for 21.6ks to remove hydrogen. Then, they were polished with 0/4 emery paper, lapped with 0.05um y-alumina dispersed on micro-cloth and washed in dehydrated methanol. Chemical compositions and tensile properties are shown in Table 1.Fatigue tests were conducted using a fatigue testing apparatus, an actual load applied to the specimen being exactly measured with an external load cell(4)(5). The fatigue testings were performed in the conditions of sinusoidal tension- Fig. 1 Shape of the specimen.
Sexually competent females of Telmessus cheiragonus (helmet crab) release two pheromones that elicit grasping and copulation behaviors in males (Kamio et al., 2000, 2002, 2003). Our study aimed to use behavioral and electrophysiological techniques to identify the site of reception of these sex pheromones. In behavioral experiments, either the inner or the outer flagella of the antennules were ablated bilaterally from male crabs, and responses of male crabs to female odor were examined. When the inner flagella were surgically ablated, the sexual response (i.e., grasping and copulation behavior) of male crabs was not significantly changed relative to control animals that had their second antennae ablated. In contrast, the sexual response was significantly reduced when the outer flagella of the antennules were ablated, suggesting that the outer flagellum is the receptor organ that detects the sex pheromones. In electrophysiological experiments, urine, which in females contains the pheromone that elicits grasping behavior by males but does not contain the pheromone eliciting copulation, whose release site is not known, was tested. Female and male urine as well as shrimp extract evoked phasic responses of chemosensory afferents innervating aesthetasc sensilla on the outer flagellum of male crabs. The response of the afferents had significantly higher magnitude and lower threshold when female urine was applied. Thus, behavioral and electrophysiological observations suggest that in male helmet crabs, the outer flagellum of the antennule is the chemosensory organ that detects female sex pheromone.
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