The relative contributions of sagittal,frontal, and transverse joint works to self-paced incline and decline slope walking

Positive and negative work are generated at the lower limb joints in order to locomote over various terrains. Joint work quantifies the changes in energy that are necessary to adapt gait to environmental demands. The aim of this study was to quantify 3D joint work at the hip, knee, and ankle during slope walking. Work was calculated for ten males (23.9 ± 1.1 years) walking at a self-selected speed on inclines and declines (−20, −12, −6, 0, 6, 12, 20 degrees). Sagittal positive work significantly increased at the hip, knee, and ankle for incline walking (for example, hip positive work increased 153%, 280%, and 453% for 6, 12, and 20 degrees, respectively; knee and ankle positive work also increased) (p ≤ 0.05), in order to raise and propel the body forward. Sagittal negative work increased significantly at the hip, knee and ankle for decline walking (for example, knee negative work increased 193%, 355%, and 496% for −6, −12, and −20 degrees, respectively; hip and ankle negative work also increased) (p ≤ 0.05), in order to control body descent. These substantial changes in work will be especially challenging for people with compromised strength due to age and disease. Furthermore, changes in work were not limited to the sagittal plane: 46% of the total hip joint work occurred in the frontal and transverse planes for six degree decline walking. Thus, decline walking placed greater demands on the hip ab/adductors and rotators, and this may be related to the greater risk of falls observed for descent versus ascent.     

A new genus from the continental slope off Brazil and the discovery of the first males in the Hirsutiidae (Crustacea: Peracarida: Bochusacea)

Montucaris distincta gen. nov. sp. nov. , a new genus and species of hirsutiid, is described from the bathyal floor of the northern South Atlantic, off Brazil. It is easily distinguished from other members of the family by the reduced, one-segmented exopods of pereopods 5 and 6 and the array of stout triangular spines present on the anterior margin of the basis and proximal endopodal segments of the third pereopod. This discovery is notable as it includes the first record of males in the family, demonstrating that hirsutiids are gonochoristic. Developmental stages including mancas, preparatory females and juvenile males were recovered, in addition to numerous brooding females and two morphs of adult males. We infer that the new genus has a life cycle involving non-feeding terminal males with regressed mouthparts. These males display a bizarre cephalic configuration, with a clearly defined transverse dorsal suture on the dorsal cephalothoracic shield just behind the articulation of mandibles, a feature present also in syncarida and in some Thermosbaenacea and that we interpret as secondary. The peracaridan affinities of the Hirsutiidae are firmly established here after settling definitively the oostegitic nature of the setose plates present on the posteromedial margin of the pereopodal coxae of brooding females. The separate ordinal rank for hirsutiids – as the Bochusacea – with respect to the Mictacea, within which they had been previously classified, is favoured here. In addition, we highlight similarities between hirustiids and tanaidaceans that warrant further investigation. © 2006 The Linnean Society of London, Zoological Journal of the Linnean Society , 2006, 148 , 169–208.     

The mechanism of Drosophila leg development along the proximodistal axis

During development of higher organisms, most patterning events occur in growing tissues. Thus, unraveling the mechanism of how growing tissues are patterned into final morphologies has been an essential subject of developmental biology. Limb or appendage development in both vertebrates and invertebrates has attracted great attention from many researchers for a long time, because they involve almost all developmental processes required for tissue patterning, such as generation of the positional information by morphogen, subdivision of the tissue into distinct parts according to the positional information, localized cell growth and proliferation, and control of adhesivity, movement and shape changes of cells. The Drosophila leg development is a good model system, upon which a substantial amount of knowledge has been accumulated. In this review, the current understanding of the mechanism of Drosophila leg development is described.     

Protein kinase CK2 is required for dorsal axis formation in Xenopus embryos

Dorsal axis formation in Xenopus embryos is dependent upon asymmetrical localization of beta-catenin, a transducer of the canonical Wnt signaling pathway. Recent biochemical experiments have implicated protein kinase CK2 as a regulator of members of the Wnt pathway including beta-catenin. Here, we have examined the role of CK2 in dorsal axis formation. CK2 was present in the developing embryo at an appropriate time and place to participate in dorsal axis formation. Overexpression of mRNA encoding CK2 in ventral blastomeres was sufficient to induce a complete ectopic axis, mimicking Wnt signaling. A kinase-inactive mutant of CK2alpha was able to block ectopic axis formation induced by XWnt8 and beta-catenin and was capable of suppressing endogenous axis formation when overexpressed dorsally. Taken together, these studies demonstrate that CK2 is a bona fide member of the Wnt pathway and has a critical role in the establishment of the dorsal embryonic axis.     

A condition for setting off ectopic waves in computational models of excitable cells

The purpose of this paper is to study the stability of steady state solutions of the Monodomain model equipped with Luo-Rudy I kinetics. It is well established that re-entrant arrhythmias can be created in computational models of excitable cells. Such arrhythmias can be initiated by applying an external stimulus that interacts with a partially refractory region, and spawn breaking waves that can eventually generate extremely complex wave patterns commonly referred to as fibrillation. An ectopic wave is one possible stimulus that may initiate fibrillation. Physiologically, it is well known that ectopic waves exist, but the mechanism for initiating ectopic waves in a large collection of cells is poorly understood. In the present paper we consider computational models of collections of excitable cells in one and two spatial dimensions. The cells are modeled by Luo-Rudy I kinetics, and we assume that the spatial dynamics is governed by the Monodomain model. The mathematical analysis is carried out for a reduced model that is known to provide good approximations of the initial phase of solutions of the Luo-Rudy I model. A further simplification is also introduced to motivate and explain the results for the more complicated models. In the analysis the cells are divided into two regions; one region (N) consists of normal cells as model by the standard Luo-Rudy I model, and another region (A) where the cells are automatic in the sense that they would act as pacemaker cells if they where isolated from their surroundings. We let delta denote the spatial diffusion and a denote a characteristic length of the automatic region. It has previously been shown that reducing diffusion or increasing the automatic region enhances ectopic activity. Here we derive a condition for the transition from stable resting state to ectopic wave spread. Under suitable assumptions on the model we provide mathematical and computational arguments indicating that there is a constant eta such that a steady state solution of this system is stable whenever delta approximately > etaa(2), and unstable whenever delta approximately < etaa(2).     

视黄酸挽救的视黄酸合成酶Raldh2基因敲除鼠E10.75胚胎后肢发育正常

视黄酸合成酶Raldh2基因敲除鼠胚胎没有肢体的发育在胚胎E6.75-E 8.25期间,喂给怀孕母鼠含视黄酸（0.1 mg/g食物）食物后,Raldh2基因敲除鼠E10.75胚胎后肢形态正常,前肢发育较小.原位杂交结果表明,决定肢体近 远端轴发育的标志基因(marker gene)Fgf8,决定前-后轴发育的标志基因Shh以及后肢发育特异性基因Tbx4 和Pitx1在视黄酸挽救的Raldh2基因敲除鼠E10.75胚胎的后肢表达正常.上述结果提示,视黄酸可以挽救Raldh2基因敲除鼠E10.75胚胎后肢的正常发育.     

EMG median frequency changes in the neck–shoulder stabilizers of symptomatic office workers when challenged by different physical stressors

The problem of work-related neck and upper limb disorders among computer users has been reported extensively in the literature, and commonly cited risk factors include static posture, speed and force of keyboard operation. The present study examined changes in median frequency (MF) of the neck–shoulder muscles in symptomatic and asymptomatic office workers when they were exposed to these three physical stressors.

A quasi-experimental Case–Control design was used to examine MF changes in two groups of female office workers when they were subjected to controlled doses of computer work involving prolonged static posture, increased typing speed and increased typing force. The MF of four major neck–shoulder muscles were examined bilaterally and compared between groups.

The MF changes over time-at-task did not clearly illustrate any muscle fatigue mechanism. However, Case Group consistently showed trends for higher MF than the Control Group, and this pattern was observed in response to all three physical stressors. The consistent group differences in MF suggest different muscle recruitment strategies between symptomatic and asymptomatic office workers. These results implied that symptomatic individuals had altered motor control, which may have important implications in understanding the etiology of work-related musculoskeletal disorders.