河野脂螨发育各阶段外部形态扫描电镜观察

【目的】了解河野脂螨Lardoglyphus konoi各发育阶段外部形态和超微结构特征。【方法】利用室内培养获得的不同发育阶段的河野脂螨个体样本,在扫描电镜下观察各发育阶段(卵、幼螨、若螨和成螨)的外部形态和超微结构。【结果】河野脂螨卵呈椭圆形;幼螨足3对,未见生殖器官生长痕迹,生殖毛和肛毛缺如;若螨足4对,生殖器官发育不完全,有生殖毛和肛毛,但发育亦不完全。休眠体前端尖细,后端钝圆,呈梨形状。在末体区有吸盘板,其上有13个吸盘,呈2-2-4-5分布。成螨螯肢细长,剪刀状,其上的定趾和动趾上有几个小齿;顶外毛长度约为顶内毛的50%,与顶内毛处同一水平线上。雄成螨第3对足的跗节末端为2个粗钝的齿所替代;腹面有1个生殖区和带有1对肛门吸盘的肛区。雌成螨所有的爪均分叉;腹面生殖孔为1个纵向裂缝;肛门不伸达后缘。【结论】通过电镜扫描对河野脂螨不同发育阶段外部形态和超微结构的观察,更加详细地了解了该螨的形态结构,从而为脂螨科螨类的分类和生物学研究提供了理论依据。     

Integration of Sugar Metabolism and Proteoglycan Synthesis by UDP-glucose Dehydrogenase

Regulation of proteoglycan and glycosaminoglycan synthesis is critical throughout development, and to maintain normal adult functions in wound healing and the immune system, among others. It has become increasingly clear that these processes are also under tight metabolic control and that availability of carbohydrate and amino acid metabolite precursors has a role in the control of proteoglycan and glycosaminoglycan turnover. The enzyme uridine diphosphate (UDP)-glucose dehydrogenase (UGDH) produces UDP-glucuronate, an essential precursor for new glycosaminoglycan synthesis that is tightly controlled at multiple levels. Here, we review the cellular mechanisms that regulate UGDH expression, discuss the structural features of the enzyme, and use the structures to provide a context for recent studies that link post-translational modifications and allosteric modulators of UGDH to its function in downstream pathways:     

Changes in muscle activation,oxygenation, and morphology following a fatiguing repetitive forward reaching task in young adult males and females

We sought to evaluate sex-specific 1) muscle activation patterns, hemodynamics, and swelling responses to short-cycle repetitive fatigue; 2) relationships between muscular responses and perceived fatigability. Asymptomatic participants (N = 26, 13 females) completed a repetitive pointing task until 8/10 on the Borg CR10 scale. Upper trapezius (UT), supraspinatus (SUPRA), and biceps brachii (BIC) muscle activation, activation variability (CV), median power frequency (MdPF) and thickness, and UT oxygenation were recorded. Males had higher BIC CV, UT and SUPRA MdPF, and UT and BIC thickness. Longer time to fatigue-terminal was correlated to greater SUPRA activation increase (ρ = 0.624) and BIC MdPF decrease (ρ = -0.674) in males, while in females it was correlated to greater (ρ = -0.657) and lower (ρ = 0.683) decrease of SUPRA and BIC CV, respectively. Male’s greater increase in SUPRA thickness correlated to greater increase in UT thickness and tissue oxygenation index, and to lower increase of UT deoxyhemoglobin. Females’ greater decrease of SUPRA MdPF correlated to greater decrease of UT MdPF, while greater UT activation increase was related to lower UT thickness increase. Results suggest that despite comparable time to fatigue-terminal, males have greater force-generating capacity and neuromuscular reliance on recruitment and excitation rates, while females have greater reliance on activation variability. Further, there are relationships between hemodynamic and swelling patterns in males, while there are relationships between activation and swelling patterns in females. Although there were no differences in experimental task-induced changes, there are sex-specific relationships between muscular patterns and perceived fatigability, which may help explain sex-specific mechanisms of musculoskeletal disorders.     

Relationship between resting medial gastrocnemius stiffness and drop jump performance

Although the influence of the series elastic element of the muscle–tendon unit on jump performance has been investigated, the corresponding effect of the parallel elastic element remains unclear. This study examined the relationship between the resting calf muscle stiffness and drop jump performance. Twenty-four healthy men participated in this study. The shear moduli of the medial gastrocnemius and the soleus were measured at rest as an index of muscle stiffness using ultrasound shear wave elastography. The participants performed drop jumps from a 15 cm high box. The Spearman rank correlation coefficient was used to examine the relationships between shear moduli of the muscles and drop jump performance. The medial gastrocnemius shear modulus showed a significant correlation with the drop jump index (jump height/contact time) (r = 0.414, P = 0.044) and jump height (r = 0.411, P = 0.046), but not with contact time (P > 0.05). The soleus shear modulus did not correlate with these jump parameters (P > 0.05). These results suggest that the resting medial gastrocnemius stiffness can be considered as one of the factors that influence drop jump performance. Therefore, increase in resting muscle stiffness should enhance explosive athletic performance in training regimens.     

Argyrophilic nucleolar organizing region associated protein synthesis in hair root cells of humans at different developmental stages and sex

Abstract

Argyrophilic nucleolar organizing region (AgNORs) associated proteins are important for cell proliferation and various diseases. We investigated AgNOR protein synthesis in hair root cells of males and females at different ages using two-dimensional image analysis. Experiments were performed on 58 healthy male and 24 healthy female volunteers in three groups according to age and sex. Hair root cells obtained from hair follicles were stained with silver. Total AgNOR number/total nuclear number (TAN/TNN) and total AgNOR area/nuclear area (TAA/NA) for each nucleus were analyzed. The only significant difference was observed in TAA/NA values for males and females from 6 to 12 years old. We suggest that the difference is due to high NOR activity caused by increased growth hormone production in hair root cells.     

Massage and stretching reduce spinal reflex excitability without affecting twitch contractile properties

Both stretching and massage can increase range of motion. Whereas the stretching-induced increases in ROM have been attributed to changes in neural and muscle responses, there is no literature investigating the ROM mechanisms underlying the interaction of stretch and massage. The objective of this paper was to evaluate changes in neural and evoked muscle responses with two types of massage and static stretching. With this repeated measures design, 30 s of plantar flexors musculotendinous junction (MTJ) and tapotement (TAP) massage were implemented either with or without 1 min of concurrent stretching as well as a control condition. Measures included the soleus maximum H-reflex/M-wave (H/M) ratio, as well as electromechanical delay (EMD), and evoked contractile properties of the triceps surae. With the exception of EMD, massage and stretch did not significantly alter triceps surae evoked contractile properties. Massage with and without stretching decreased the soleus H/M ratio. Both TAP conditions provided greater H/M ratio depression than MTJ massage while the addition of stretch provided the greatest inhibition. Both massage types when combined with stretching increased the duration of the EMD. In conclusion, MTJ and TAP massage as well as stretching decreased spinal reflex excitability, with TAP providing the strongest suppression. While static stretching prolongs EMD, massage did not affect contractile properties.     

Interaction against different environmental dynamics during a leg extension task is controlled by temporal rather than amplitude scaling of muscular activity

Force exertion against different mechanical environments can affect motor control strategies in order to account for the altered environmental dynamics and to maintain the ability to produce force. Here, we investigated the change of muscular activity of selected muscles of the lower extremities while the participants interacted with an external mechanical device of variable stability. Twenty-five healthy participants exerted force against the device by performing a unilateral ballistic leg extension task under 1 or 3 degrees of freedom (DoF). Directional force data and electromyographic responses from four leg muscles (TA, VM, GM, PL) were recorded. Muscle responses to the altered experimental conditions were analyzed by calculating time to peak electrical activity (TTP), peak electrical activity (PEA), slope of EMG-signal and muscle activity. It was found that neuromuscular system adjustments to the task are expressed mainly by temporal (TTP) rather than amplitude (PEA) scaling of muscular activity. This change was specific for the investigated muscles. Moreover, a selective increase of muscle activity occurred while increasing external DoF. This scheme was accompanied by a significant reduction of applicable force against the device in the unstable 3 DoF condition. The findings suggest that orchestration of movement control is linked to environmental dynamics also affecting the ability to produce force under dynamic conditions. The adjustments of the neuromuscular system are rather temporal in nature being consistent with the impulse timing hypothesis of motor control.     

Does interhemispheric communication relate to the bilateral function of muscles? A study of scapulothoracic muscles using transcranial magnetic stimulation

Interhemispheric connections have been demonstrated between the motor cortex controlling muscle pairs. However, these investigations have tended to concentrate upon hand muscles. We have extended these investigations to proximal muscles that control the scapula upon the trunk and help to move and stabilise the shoulder. Using a paired pulse transcranial magnetic stimulation protocol, the interhemispheric interactions between different shoulder girdle muscle pairs, serratus anterior, upper trapezius and lower trapezius were investigated. Test motor evoked potentials were conditioned using conditioning pulse intensities of 80% and 120% of active motor threshold at three different condition-test intervals, during three different tasks. Interhemispheric inhibition was observed in upper trapezius using a conditioning intensity of 120% and condition-test interval of 8 ms (17 ± 18%, p < 0.007). A trend towards inhibition was observed in lower trapezius and serratus anterior using a conditioning intensity of 120% and a condition-test interval of 8 ms (13 ± 22%; p < 0.07 and 10 ± 19% respectively; p < 0.07). No interhemispheric facilitation was evoked. The study demonstrates that a low level of interhemispheric inhibition rather than interhemispheric facilitation could be evoked between these muscle pairs.     

Effects of coupled upper limbs movements on postural stabilisation

The preference for in-phase association of coupled cyclic limbs movements is well described (mirror-symmetrical patterns) and this is demonstrated by the ease of performing in-phase movements compared to anti-phase ones. The hypothesis of this study is that the easiest movement patterns are those with minor postural activity. The aim of this study was to describe postural activity in standing subjects in the sagittal and frontal planes during the execution of three upper limbs tasks (single arm, in-phase, anti-phase) at four different frequencies (from 0.6 to 1.2 Hz).We employed six infrared cameras for recording kinematics information, a force platform for measuring forces exerted on the ground, and a system for surface electromyography (SEMG). Outcome measures were: upper limb range of movement and relative-phase, centre of pressure displacement (COP), screw torque (T_z) exerted on the ground, and SEMG recordings of postural muscles (adductor longus, gluteus medius, rectus femoris, and biceps femoris).Our results show that in both the planes the in-phase task resulted in less COP displacement, torque production, and postural muscles involvement than the anti-phase and single arm tasks. This reduced need of postural control could explain the ease of performing in-phase coupled limb movements compared with anti-phase movements.