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Caudal Regions (caudal + regions)
Selected AbstractsMotor units in cranial and caudal regions of the upper trapezius muscle have different discharge rates during brief static contractionsACTA PHYSIOLOGICA, Issue 4 2008Roberto Merletti No abstract is available for this article. [source] Motor units in cranial and caudal regions of the upper trapezius muscle have different discharge rates during brief static contractionsACTA PHYSIOLOGICA, Issue 4 2008D. Falla Abstract Aim:, To compare the discharge patterns of motor unit populations from different locations within the upper trapezius muscle during brief submaximal constant-force contractions. Methods:, Intramuscular and surface electromyographic (EMG) signals were collected from three sites of the right upper trapezius muscle distributed along the cranial-caudal direction in 11 volunteers during 10 s shoulder abduction at 25% of the maximum voluntary force. Results:, A total of 38 motor units were identified at the cranial location, 36 from the middle location and 17 from the caudal location. Initial discharge rate was greatest at the caudal location (P < 0.05; mean ± SD, cranial: 16.7 ± 3.6 pps, middle: 16.9 ± 4.0 pps, caudal: 19.2 ± 3.3 pps). Discharge rate decreased during the contraction for the most caudal location only (P < 0.05). Initial estimates of surface EMG root mean square values were highest at the most caudal location (P < 0.05; cranial: 32.3 ± 20.9 ,V, middle: 41.3 ± 21.0 ,V, caudal: 51.6 ± 23.6 ,V). Conclusion:, This study demonstrates non-uniformity of motor unit discharge within the upper trapezius muscle during a brief submaximal constant-force contraction. Location-dependent modulation of discharge rate may reflect spatial dependency in the control of motor units necessary for the development and maintenance of force output. [source] Early requirement for fgf8 function during hindbrain pattern formation in zebrafishDEVELOPMENTAL DYNAMICS, Issue 2 2004Elizabeth L. Wiellette Abstract Fibroblast growth factor (FGF) signaling is required for normal development of the vertebrate brain, including the isthmus and caudal regions of the hindbrain. Recent work in zebrafish has identified a requirement for the combination of fgf3 and fgf8 functions in specification of rhombomeres 5 and 6 (r5, r6), when evaluated at mid- and late somitogenesis stages. However, when examined earlier in development, during early somitogenesis stages, FGF8 alone is required to initiate r5 and r6 development. Both a mutation in fgf8 and injection of fgf8 -targeted antisense morpholino-modified oligonucleotides result in suppression of genes normally expressed in r5 and r6 by the one- to two-somite stage. This expression recovers by the six-somite stage, and we propose that this recovery is a response to activation of fgf3 and to delayed accumulation of fgf8. These data demonstrate an early, nonredundant requirement for fgf8 function in hindbrain patterning. Developmental Dynamics 229:393,399, 2004. © 2004 Wiley-Liss, Inc. [source] Effects of size and morphology on swimming performance in juvenile brown trout (Salmo trutta L.)ECOLOGY OF FRESHWATER FISH, Issue 4 2003A. F. Ojanguren Abstract,,, Our study assesses swimming capacity (speed and stamina) and possible morphometric determinants of locomotor performance of juvenile brown trout (Salmo trutta L.). We addressed these issues at the individual level to have an approach of the functional significance of intraspecific variation in morphological design. Both swimming speed and endurance time showed significant positive relationships with fish length. Size-corrected values of speed and endurance time were negatively correlated suggesting a phenotypic trade-off between burst and prolonged swimming. Size was also highly correlated with all the morphological variables measured. Therefore, we used the residuals of the regressions of those variables on fish length to remove the effect of body size. A principal components analysis (PCA) summarised the 12 morphological variables into two factors, which accounted for 44.3% of the variance. PC1 combined several measures of body depth and width, whereas PC2 represented mainly postanal length relative to abdomen length. Relationships between the scores of the two factors and size-corrected values of maximum swimming speed and endurance time were weak. PC2 showed a significant positive relationship with endurance time; that is, individuals with longer caudal regions were able to swim against water flow for longer periods of time. Stoutness (PC1) showed a marginally significant negative correlation with endurance time. The lack of stronger relationships could be because of the low morphometric variability among the test individuals, all proceeding from the same population, reared in a common environment, and measured at the same ontogenetic stage. [source] The organization of visual object representations: a connectionist model of effects of lesions in perirhinal cortexEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2002Timothy J. Bussey Abstract We have developed a simple connectionist model based on the idea that perirhinal cortex has properties similar to other regions in the ventral visual stream, or ,what' pathway. The model is based on the assumption that representations in the ventral visual stream are organized hierarchically, such that representations of simple features of objects are stored in caudal regions of the ventral visual stream, and representations of the conjunctions of these features are stored in more rostral regions. We propose that a function of these feature conjunction representations is to help to resolve ,feature ambiguity', a property of visual discrimination problems that can emerge when features of an object predict a given outcome (e.g. reward) when part of one object, but predict a different outcome when part of another object. Several recently reported effects of lesions of perirhinal cortex in monkeys have provided key insights into the functions of this region. In the present study these effects were simulated by comparing the performance of connectionist networks before and after removal of a layer of units corresponding to perirhinal cortex. The results of these simulations suggest that effects of lesions in perirhinal cortex on visual discrimination may be due not to the impairment of a specific type of learning or memory, such as declarative or procedural, but to compromising the representations of visual stimuli. Furthermore, we propose that attempting to classify perirhinal cortex function as either ,perceptual' or ,mnemonic' may be misguided, as it seems unlikely that these broad constructs will map neatly onto anatomically defined regions of the brain. [source] ADAPTIVE MIGRATORY DIVERGENCE AMONG SYMPATIRIC BROK CHARR POPULATIONSEVOLUTION, Issue 3 2005Dylan J. Fraser Abstract Ecological processes clearly contribute to population divergence, yet how they interact over complex life cycles remains poorly understood. Notably, the evolutionary consequences of migration between breeding and nonbreeding areas have received limited attention. We provide evidence for a negative association between interpopulation differences in migration (between breeding and feeding areas, as well as within each) and the amount of gene flow (m) among three brook charr (Salvelinus fontinalis) populations inhabitingMistassini Lake, Quebec, Canada. Individuals (n=1166) captured throughout lake feeding areas over two consecutive sampling years were genotyped (10 microsatellites) and assigned to one of the three populations. Interpopulation differences in migration were compared based on spatial distribution overlap, habitat selection, migration distance within feeding areas, and morphology. We observed a temporally stable, heterogeneous spatial distribution within feeding areas among populations, with the extent of spatial segregation related to differential habitat selection (represented by littoral zone substrate). Spatial segregation was lowest and gene flow highest (m=0.015) between two populations breeding in separate lake inflows. Segregation was highest and gene flow was lowest (mean m=0.007) between inflow populations and a third population breeding in the outflow. Compared to outflow migrants, inflow migrants showed longer migration distances within feeding areas(64,70 km vs. 22 km). After entering natal rivers to breed, inflow migrants also migrated longer distances (35,75 km) and at greater elevations (50,150 m) to breeding areas than outflow migrants (0,15 km; ,10,0 m). Accordingly, inflow migrants were more streamlined with longer caudal regions, traits known to improve swimming efficiency. There was no association between the geographic distance separating population pairs and the amount of gene flow they exchanged. Collectively, our results are consistent with the hypothesis that reduced gene flow between these brook charr populations results from divergent natural selection leading to interpopulation differences in migration. They also illustrate how phenotypic and genetic differentiation may arise over complex migratory life cycles. [source] Connections of the zona incerta to the reticular nucleus of the thalamus in the ratJOURNAL OF ANATOMY, Issue 2 2006Safiye Çavdar Abstract This study demonstrated that there is a pathway from the zona incerta to the thalamic reticular nucleus. Injections of horseradish peroxidase or Fluorogold were made, using stereotaxic coordinates, into the rostral, intermediate or caudal regions of the thalamic reticular nucleus of adult Sprague,Dawley rats. The results show that the different regions of the thalamic reticular nucleus have distinct patterns of connections with the sectors of the zona incerta. In terms of the relative strength of the connections, injections made into the rostral regions of the thalamic reticular nucleus showed the highest number of labelled cells within the rostral and ventral sectors of the zona incerta; injections made into the intermediate regions of the thalamic reticular nucleus showed labelled cells in the dorsal and ventral sectors; while injections to the caudal regions of the thalamic reticular nucleus showed only a few labelled cells in the caudal sector of the zona incerta. Previous studies have shown that the zona incerta projects to the higher order thalamic nuclei but not first order thalamic nuclei. The labelling observed in the present study may represent collaterals of zona incerta to higher order thalamic nuclei projections. [source] Changes in the connections of the main olfactory bulb after mitral cell selective neurodegenerationJOURNAL OF NEUROSCIENCE RESEARCH, Issue 11 2007Javier S. Recio Abstract The connections of the main olfactory bulb (OB) of the mouse were studied with iontophoretic injections of biotinylated dextran amine. To sort efferences from mitral cells and tufted cells, the Purkinje cell degeneration (PCD) mouse was used. This mutant animal undergoes a specific neurodegeneration of mitral cells, whereas tufted cells do not degenerate. The unilateral tracer injections used were small and confined largely to the OB of both PCD and control mice at P120. Seven days after tracer injection, the efferences from the OB and the centrifugal afferences from secondary olfactory structures to it were studied. Although there is a large overlap of their target fields, mitral cell axons innervated more caudal regions of the olfactory cortex than tufted cell axons, thus providing definitive evidence of the differential projections of olfactory output neurons. Additionally, an important increase in retrogradely-labeled neurons was detected in the ipsilateral anterior olfactory nucleus of the mutant animals. This was not observed in any other secondary olfactory structure, suggesting a strengthening of the centrifugal input to the OB from that central area after mitral cell loss. Moreover, we recorded a complete loss of bilaterality in the olfactory connections of the PCD mice due to degeneration of the anterior commissure. These results point to an important reorganization of this essential olfactory circuit between the anterior olfactory nucleus and the OB, and hint at a transsynaptic level of plasticity not considered previously in literature. © 2007 Wiley-Liss, Inc. [source] A Morphological Study of Skeletal Development in Turkey during the Pre-Hatching StageANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 1 2009S. H. Atalgin Summary Skeletal chondrofication, ossification and growth of turkey embryos were investigated and analysed to enable assessment of the developmental status and evaluation of the experimental effects on skeletal development, skeletal mutations and development of cultured embryos. Ten embryos were prepared every 24 h from 8 to 28 days of incubation. The fixed embryos were cleared and stained in toto with Alcian blue & Alizarin red for cartilage and ossified components, respectively. Observation of the skeleton was performed under a stereoscopic microscopy, with special attention to the timing of chondrofication and ossification of the bones. The first occurrence of the primary ossification centres was observed in the femur, tibiotarsus, and the dentary and supra-angular of the mandible on the 12th day, followed immediately by the other long bones. Skeletal features of the skull were determined to show the latest appearance of cartilage and ossification. Hence, all elements of the hyolingual apparatus remained cartilaginous until hatching took place except for the ceratobranchial. Even though the vertebral column chondrified earlier as compared with the ribs and sternum, they ossified later. While chondrofication was present in all the regions of the vertebral column at the same time, ossification progressed from the cervical through caudal regions. The growth rate of the femur was eminently higher than that of the humerus with increase in time, particularly after the 20th day of incubation. This seems to be obviously natural because the eggs used in the study are from the broiler turkey, which gains giant muscle mass at a very short period; precocity is probably at the expense of the bones of the leg rather than those of the wing. [source] Development of deformities at the vertebral column in Diplodus sargus (L., 1758) early larval stagesAQUACULTURE RESEARCH, Issue 7 2010Margarida Saavedra Abstract One of the bottleneck problems of Diplodus sargus farming is a high incidence of skeletal deformities at the vertebral column. In this study, the pattern of vertebral deformities were determined in three different larval batches from 2 to 30 days after hatching (DAH). During this period, 60 larvae per spawn were observed at 2, 8, 13, 15, 18, 21, 23, 25, 27 and 30 DAH and the different types and frequency of vertebral column malformations were registered. Deformities started from 8 to 13 DAH, when the percentage of deformed larvae rose from approximately 5% to 40%. At 15 DAH, skeletal malformations had frequencies up to 80% of the observed larvae. Serious malformations such as kyphosis, scoliosis and lordosis were observed at 18 DAH but seldom in percentages higher than 15%. Vertebral fusions and compressions especially affected the preurostyle region. Abnormal shape vertebrae were more frequent between vertebrae 15 and 21. Other malformations observed were hypertrophic vertebrae, more common in the trunk and caudal regions, reaching percentages higher than 50% in the former. This study has useful information concerning skeletal malformations at the vertebral column of D. sargus larvae, as it identifies the main deformities observed and the ages of highest incidence. [source] Heritability and genetic correlation of abdominal versus caudal vertebral number in the medaka (Actinopterygii: Adrianichthyidae): genetic constraints on evolution of axial patterning?BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2009KAZUNORI YAMAHIRA Variation in the number of abdominal vs. caudal vertebrae is an important source of morphological diversification of fish. It is not clear, however, whether abdominal and caudal regions evolve independently. Regressions of offspring on parents demonstrated substantial additive genetic variation within populations, i.e. heritability, in both abdominal and caudal vertebral numbers of the medaka (Oryzias latipes). However, the heritability of caudal vertebrae tended to be smaller than that of abdominal vertebrae in some estimations, suggesting that abdominal and caudal regions are controlled by separate developmental modules. Furthermore, genetic correlation between abdominal and caudal vertebral numbers, estimated using full-sib family means, was negative but weak, supporting independent evolution. In addition, substantial genetic differentiation among populations was demonstrated in abdominal vertebral numbers, but not in caudal numbers. These results support our view that Jordan's rule, a geographical tendency for fish from higher latitudes to have more vertebrae, in this fish reflects local adaptations of abdominal vertebral numbers. In contrast, the low heritability of caudal vertebrae may reflect the intrinsic invariability of genes associated with a change in caudal vertebral numbers. This genetic constraint may have restricted morphological diversification of not only the medaka, but also the Order Beloniformes as a whole. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96, 867,874. [source] | |||||||||||||||||||