Artificial selection sheds light on developmental mechanisms of limb elongation

Species diversity in limb lengths and proportions is thought to have evolved adaptively in the context of locomotor and habitat specialization, but the heritable cellular processes that drove this evolution within species are poorly understood. In this study, we take a novel “micro‐evo‐devo” approach, using artificial selection on relative limb length to amplify phenotypic variation in a population of mice, known as Longshanks, to examine the cellular mechanisms of postnatal limb development that contribute to intraspecific limb length variation. Cross‐sectional growth data indicate that differences in bone length between Longshanks and random‐bred controls are not due to prolonged growth, but to accelerated growth rates. Histomorphometric and cell proliferation assays on proximal tibial growth plates show that Longshanks’ increased limb bone length is associated with an increased number of proliferative chondrocytes. In contrast, we find no differences in other growth plate cellular features known to underlie interspecific differences in limb bone size and shape, such as the rates of chondrocyte proliferation or the size and number of hypertrophic cells in the growth plate. These data suggest that small differences among individuals in the number of proliferating chondrocytes are a potentially important determinant of selectable intraspecific variation in individual limb bone lengths, independent of body size.     

Combined effects of aging and obesity on postural control,muscle activity and maximal voluntary force of muscles mobilizing ankle joint

ObjectiveThe aim of the study was to investigate the influence of age and/or obesity on postural control, ankle muscle activities during balance testing and force production capacities.Materials and methods4 groups; control group (CG; n = 25; age = 31.8 ± 7.5 years; BMI = 21.4 ± 2.5 kg/m²), obese group (OG; n = 25; age = 34.4 ± 9.5 years; BMI = 39.6 ± 5.4 kg/m²), elderly group (EG; n = 15; age = 77.1 ± 8.4 years; BMI = 24.4 ± 1.3 kg/m²) and obese elderly group (ObEG; n = 12; age = 78.6 ± 6.6 years; BMI = 34.5 ± 3.1 kg/m²) performed maximal voluntary contraction (MVC) before testing to calculate the maximal relative force of ankle plantar flexor (PF) and dorsal flexor (DF) muscles. Center of pressure (CoP) parameters and the electromyography (EMG) activity of PF and DF muscles were collected during MVC, quiet standing and limit of stability (LoS) testing along antero-posterior and medio-lateral axes.ResultsMaximal relative force was higher in EG and ObEG than CG and OG, respectively (p < 0.001). CoP parameters, distance traveled along the antero-posterior axis and EMG activity of PF were higher in OG, EG and ObEG compared to CG (p < 0.001) and in EG compared to ObEG (p < 0.05).The EMG activity of PF was positively correlated with CoP parameters in OG and ObEG (r > 0.6; p < 0.05). Maximal relative force of PF (r > −0.6; p < 0.05) was negatively correlated with CoP parameters in ObEG and EG.ConclusionObesity-related postural control alteration is associated with increased activity of PF. This neuromuscular adaptation may reflect deteriorations of the proprioceptive system and is likely additional to age-related muscular impairments. This may be a mechanism by which obesity increases postural control alterations in elderly.     

Influence of gait speed on free vertical moment during walking

Free vertical moment (FVM) of ground reaction is recognized to be a meaningful indicator of torsional stress on the lower limbs when walking. The purpose of this study was to examine whether and how gait speed influences the FVM when walking. Fourteen young healthy adults performed a series of overground walking trials at three different speeds: low, preferred and fast. FVM was measured during the stance phase of the dominant leg using a force platform embedded in a 10 m-long walkway. Transverse plane kinematic parameters of the foot and pelvis were measured using a motion capture system. Results showed a significant decrease in peak abduction FVM (i.e., resisting internal foot rotation) and an increase in peak adduction FVM (i.e., resisting external foot rotation), together with an increase in gait speed. Concomitantly, we observed a decrease in the foot progression angle and an increase in the peak pelvis rotation velocity in the transverse plane with an increase in gait speed. A significant positive correlation was found between the pelvis rotation velocity and the peak adduction moment, suggesting that pelvis rotation influences the magnitude of adduction FVM. Furthermore, we also found significant correlations between the peak adduction FVM and both the step length and frequency, indicating that the alterations in FVM may be ascribed to changes in these two key variables of gait speed. These speed-related changes in FVM should be considered when this parameter is used in gait assessment, particularly when used as an index for rehabilitation and injury prevention.     

不同氧浓度对骨髓源内皮祖细胞分泌促血管新生相关生长因子的影响

目的:观察培养环境不同氧浓度对骨髓源内皮祖细胞分泌促血管新生相关生长因子的影响。方法:利用密度梯度离心技术分离SD大鼠骨髓单个核细胞,向内皮祖细胞进行诱导分化、扩增、培养和鉴定。然后在不同氧浓度(1%,5%,21%)的环境中培养,于第3天,7天,10天采用酶联免疫吸附试验检测内皮祖细胞分泌血管内皮生长因子(Vascular endothelial growth factor,VEGF)、基质细胞衍生因子-1α(Stromal-derived factor-1α, SDF-1α)、胰岛素样生长因子I(Insulin-like growth factor-I, IGF-I)等生长因子的水平。结果:第3天,不同氧浓度下各组EPC分泌VEGF、SDF-1α、IGF-I无明显差异(P均0.05)。第7天和第10天,各组EPC分泌IGF-I无明显差异(P均0.05);但是和21%氧浓度相比,相对低氧浓度(1%和5%)能够明显增强EPC分泌VEGF和SDF-1α(P均0.001)。结论:适当时间的低氧环境培养能够显著刺激内皮祖细胞分泌VEGF和SDF-1α,进而增强其促血管新生能力。     

Body Mass Estimates in Extinct Mammals from Limb Bone Dimensions: the Case of North American Hyaenodontids

The body mass estimation of several limb bone dimensions (shaft cross-sectional properties, articular sizes, and bone lengths) were examined using bivariate linear regression analyses. The sample included taxonomically and behaviourally diverse small to medium-sized Recent carnivorans and carnivorous marsupials. All examined limb bone dimensions indicated low errors (percentage standard error of estimate, 8–13) for the body mass estimations. Among them, humeral and femoral shaft properties correlated best with body weight, while limb bone lengths gave larger errors. Both humeral and femoral head dimensions have relatively large individual variations, and distal humeral articular dimensions seem to be influenced more by phylogenetic differences. The regressions based on each locomotor group gave slightly lower errors than those based on the total pooled sample. The results were then applied to hyaenodontid creodonts from the Eocene–Oligocene of North America. The estimated body masses (kg) are: Arfia , 5.4–9.5; Prototomus , <6.0; Pyrocyon , 2.6; Sinopa , 1.3–1.4; Tritemnodon , 7.6–13; Prolimnocyon , 1.6; Thinocyon , 0.7–2.5; Machaeroides , 12; Limnocyon , 7.8– 16; Hyaenodon , 9.1–43. The various limb bone dimensions give different body mass values, but the variation in estimates is smaller compared to those derived from dental or cranial measurements.     

Msx1‐2 immunolocalization in the regenerating tail of a lizard but not in the scarring limb suggests its involvement in the process of regeneration

The immunolocalization of the muscle segmental homoeobox protein Msx1‐2 of 27–34 kDa in the regenerating tail blastema of a lizard shows prevalent localization in the apical ependyma of the regenerating spinal cord and less intense labelling in the wound epidermis, in the apical epidermal peg (AEP), and in the regenerating segmental muscles. The AEP is a micro‐region of the regenerating epidermis located at the tail tip of the blastema, likely corresponding to the AEC of the amphibian blastema. No immunolabelling is present in the wound epidermis and scarring blastema of the limb at 18–21 days of regeneration, except for sparse repairing muscles. The presence of a proximal–distal gradient of Msx1‐2 protein, generated from the apical ependyma, is suggested by the intensity of immunolabelling. The AEP and the ependyma are believed to induce and maintain tail regeneration, and this study suggests that Msx1‐2 proteins are components of the signalling system that maintains active growth of the tail blastema. The lack of activation and production of Msx1‐2 protein in the limb are likely due to the intense inflammatory reaction following amputation. This study confirms that, like during regeneration in fishes and amphibians, also the blastema of lizards utilizes common signalling pathways for maintaining regeneration.     

Trabecular architecture and joint loading of the proximal humerus in extant hominoids,Ateles, and Australopithecus africanus

Objectives

Several studies have investigated potential functional signals in the trabecular structure of the primate proximal humerus but with varied success. Here, we apply for the first time a “whole‐epiphyses” approach to analysing trabecular bone in the humeral head with the aim of providing a more holistic interpretation of trabecular variation in relation to habitual locomotor or manipulative behaviors in several extant primates and Australopithecus africanus.

Materials and methods

We use a “whole‐epiphysis” methodology in comparison to the traditional volume of interest (VOI) approach to investigate variation in trabecular structure and joint loading in the proximal humerus of extant hominoids, Ateles and A. africanus (StW 328).

Results

There are important differences in the quantification of trabecular parameters using a “whole‐epiphysis” versus a VOI‐based approach. Variation in trabecular structure across knuckle‐walking African apes, suspensory taxa, and modern humans was generally consistent with predictions of load magnitude and inferred joint posture during habitual behaviors. Higher relative trabecular bone volume and more isotropic trabeculae in StW 328 suggest A. africanus may have still used its forelimbs for arboreal locomotion.

Discussion

A whole‐epiphysis approach to analysing trabecular structure of the proximal humerus can help distinguish functional signals of joint loading across extant primates and can provide novel insight into habitual behaviors of fossil hominins.

     

舒芬太尼复合小剂量咪达唑仑在下肢骨折椎管内麻醉前的应用观察

目的观察舒芬太尼复合小剂量咪达唑仑在下肢骨折椎管内麻醉前的应用效果。方法选取我院收治的下肢骨折患者450例,采取数字随机法分为观察组和对照组。对照组在椎管内麻醉前给予小剂量咪达唑仑,观察组在对照组的基础上于椎管麻醉前加用舒芬太尼,比较两组的应用效果。结果观察组给药后收缩压(SBP)、舒张压(DBP)、心率(HR)水平均低于入室时(P0.05),而且也明显低于对照组(P0.05)。两组血氧饱和度(SpO2)水平在入室时、给药后比较,差异无统计学意义(P0.05)。观察组给药后30、45min的镇静、镇痛效果评分均高于对照组(P0.05),而且观察组给药后45min的镇静、镇痛效果评分低于给药后30min(P0.05)。结论舒芬太尼复合小剂量咪达唑仑在下肢骨折椎管内麻醉前的应用效果显著,可达到镇静、止痛作用。     

Postcranial remains of Baphetes and their bearing on the relationships of the Baphetidae (= Loxommatidae)

The first unequivocal postcranial remains of baphetids (= loxommatids) associated with skull roof and lower jaw material are reported from a specimen of Baphetes from the English Upper Carboniferous, Duckmantian. Characters of the mandible, including the incorporation in the symphysis of paired parasymphysial plates, permit the identification of a previously indeterminate jaw from the Langsettian (Westphalian A) of Nova Scotia, as baphetid. The postcranial remains include vertebrae, pectoral and pelvic limb and limb girdle elements that present a combination of unique characters extending the diagnosis of the family Baphetidae, together with plesiomophic and derived characters which suggest that baphetids are primitive stem group tetrapods.