Multi-joint limbs permit a flexible response to unpredictable events

The human arm is kinematically redundant, which may allow flexibility in the execution of reaching movements. We have compared reaching movements with and without kinematic redundancy to unpredictable double-step targets. Subjects sat in front of a digitising tablet and were able to view an arc of four targets reflected in the mirror as virtual images in the plane of the tablet. They were instructed to move, from a central starting point, in as straight a line as possible to a target. In one-third of trials, the target light switched to one of its neighbours during the movement. Subjects made 60 movements using shoulder, elbow and wrist and then another 60 movements in which only shoulder and elbow movement were allowed. By restraining the wrist, the limb was made non-redundant. The path length was calculated for each movement. In single-step trials, there was no significant difference between path lengths performed with and without wrist restraint. As expected there was a significant increase in path length during double-step trials. Moreover this increase was significantly greater when the wrist was restrained. The variability across both single- and double-step movements was significantly less while the wrist was restrained. Importantly the performance time of the movements did not alter significantly for single-step, double-step or restrained movements. These results suggest that the nervous system exploits the intrinsic redundancy of the limb when controlling voluntary movements and is therefore more effective at reprogramming movements to double-step targets. Received: 24 March 1997 / Accepted: 7 July 1997     

大气中不同粒径颗粒物诱导人羊膜FL细胞UDS的研究

本研究以诱导人羊膜细胞ＵＤＳ为指标，对太原市大气不同粒径的颗粒物提取液进行了致突变性检验，结果表明，不同粒径颗粒物的提取液均可产生一定的遗传毒性，尤以３．３μｍ以下的颗粒物的遗传毒性较强。     

Human Y-79 retinoblastoma cells express functional corticotropin-releasing hormone receptors

In human Y-79 retinoblastoma cells corticotropin-releasing hormone (CRH) produces a marked and rapid increase of adenylate cyclase activity. The concentration of the peptide producing half-maximal stimulation is 60 nM. The effect of CRH is significantly antagonized by the specific CRH receptor antagonist alpha-helical CHR 9-41 and is mimicked by sauvagine and urotensin I, two peptides displaying sequence homology with CRH. These results demonstrate the presence of functional CRH receptors in human Y-79 retinoblastoma cells and suggest that this cell line may be a suitable model in which to study the action of CRH on human retinal cell function.     

Evidence for the presence of substance P-like immunoreactivity in the human cerebellum

Preliminary results on the localization of substance P-like immunoreactivity in the human cerebellum are presented. Cerebella from newborn and adult subjects were examined. While only sporadic positive fibres were detected in the adult tissue, the immunoreactive material appeared more abundant in the cerebella from newborn subjects. Varicose and non-varicose fibres and dot-like nerve terminals were present with different density in various regions. The paucity of immunoreactive perikarya suggests that most of the cerebellar substance P-like immunoreactive material has an extrinsic origin.     

Peak velocities of visually and nonvisually guided saccades in smooth-pursuit and saccadic tasks

 Smooth pursuit typically includes corrective catch-up saccades, but may also include such intrusive saccades away from the target as anticipatory or large overshooting saccades. We sought to differentiate catch-up from anticipatory and overshooting saccades by their peak velocities, to see whether the higher velocities of visually rather than nonvisually guided saccades in saccadic tasks may be found also in saccades in pursuit. In experiment 1, 12 subjects showed catch-up, anticipatory, and overshooting saccades to comprise 70.4% of all saccades in pursuit of periodic, 30°/s constant-velocity targets. Catch-up saccades were faster than the others. Saccadic tasks were run as well, on 19 subjects, including the 12 whose pursuit data were analyzed, with target-onset, target-remaining (saccade to the remaining target when the other three extinguish), and antisaccade tasks. For 17 of the 19 subjects, antisaccade velocities were lower than for either target-onset or target-remaining tasks. Velocities for the target-remaining task were near those for target onset, indicating that target presence, not its onset, defines visually guided saccades. Error and reaction-time data suggest greater cognitive difficulty for target remaining than for target onset, so that the cognitive difficulty of typical nonvisually guided saccade tasks is not sufficient to produce their lowered velocity. To produce reliably, in each subject, catch-up and anticipatory saccades with comparable amplitude distributions, nine new subjects were asked in experiment 2 to make intentional catch-up and anticipatory saccades in pursuit, and were presented with embedded target jumps to elicit catch-up saccades, all with periodic target trajectories of 15°/s and 30°/s. Velocities of intentional anticipatory saccades were lower than velocities of intentional catch-up saccades, while velocities of intentional and embedded catch-up saccades were similar. Target-onset and remembered-target saccadic tasks were run, showing the expected higher velocity for the target-onset task in each subject. Both experiments demonstrate higher peak velocities for catch-up saccades than for anticipatory saccades, suggesting that cortical structures preferentially involved in nonvisually guided saccades may initiate the anticipatory and overshooting saccades in pursuit. Received: 1 December 1995 / Accepted: 25 February 1997     

Morphologic characterization of osteoblast-like cell cultures isolated from newborn rat calvaria

Summary Two methods for harvesting osteoblast-like cell populations from newborn (10 days) rat calvaria were compared. The first one consisted in culturing the periosteum-free bones and then trypsinizing the cells on the bone surface. The second one involved the migration of the osteoblasts on glass fragments before trypsinization. Since the plating efficiency, the proportion of alkaline phosphatase-positive cells, the population doubling time, and the calcium deposition were more adequate, the second method was used to further characterize the behavior of the cultures. During the first week of culture, the cells featured shapes similar to those observedin vivo on the surface of periosteum-free calvaria. They formed multilayers and, in the presence of ascorbic acid, synthetized an organic matrix containing exclusively type I collagen. Later, small amounts of type III collagen appeared. The cells were embedded in the matrix and progressively acquired the morphologic phenotype of osteocyte-like cells. The matrix mineralized in the presence of β-glycerophosphate. The technique of dropinoculation (high concentration of cells in a small volume of medium) promoted the multilayer formation and the achievement of large mineralized plates (about 1 cm²) in 3 weeks of culture.     

人心房肌细胞特殊颗粒的电镜酶细胞化学和免疫电镜研究

本研究应用电镜CMP酶细胞化学和心钠素免疫电镜胶体金,分别标记人心房肌细胞中初级溶酶体和心钠素,进行鉴别定位观察和定量分析。心钠素颗粒数量居多,占78.7～79.3％,大小均一,直径0.20±0.05μm(x±s),分布于整个细胞质内,多成簇,尤以肌膜下,核极区多见。而溶酶体大小不一,直径0.30±0.19μm(x±s),显著大于心钠素颗粒(P<0.001),一般在核极区成簇分布,也见肌原纤维之间和肌膜下单个散在分布。     

短发夹状RNA对PC-3M细胞端粒酶逆转录酶基因表达和端粒酶活性的影响

目的:研究短发夹状RNA(shRNA)对PC 3M细胞中端粒酶逆转录酶(hTRT)基因表达及端粒酶活 性的影响。方法:构建针对hTRT基因的shRNA表达质粒psilencer TRT,在质脂体介导下转染人前列腺癌PC 3M细胞,应用RT PCR及免疫组织化学检测hTRTmRNA及蛋白表达水平,应用SYBR Green染色法检测端粒 酶活性的变化。结果:重组体psilencer TRT转染细胞24h和48h后显著下调hTRTmRNA及蛋白水平,作用 48h后,其抑制率分别为85.39%和79.17%,较空白对照组差异有统计学意义(P<0.01)。同时,随着时间的延 长,端粒酶活性亦有明显下降(P<0.01)。结论:利用短发夹状RNA干扰技术能有效抑制靶基因的表达,为前 列腺癌的基因治疗提供新思路。     

增龄后成骨细胞和破骨细胞的生物学特性

骨质疏松或增龄性骨丢失与老年人成骨细胞和破骨细胞的功能特点密切相关。尽管高龄人群成骨细胞骨形成作用和破骨细胞骨吸收作用对骨骼的影响都逐渐下降,但表现出不同的特点。(1)骨形成功能持续降低,主要表现为:成骨细胞分裂增生能力降低、基质合成减少、对钙调激素的敏感性降低。这些变化与骨髓中前体细胞的快速减少有关,使高龄人群骨骼中成骨细胞群由于缺乏新生细胞的不断补充而功能退化。(2)骨吸收功能短暂激活,主要表现为:破骨细胞数量一度增加,而其泌酸和蛋白酶功能基本得以保持。(3)成骨细胞调节能力降低,主要表现为成骨细胞中RANKL和OPC表达失偶联。破骨细胞激活的机制和破骨细胞二次活跃产生不同骨平衡的意义值得探讨。作为建议,我们提倡在基础领域重视骨髓微环境中前体细胞分化增殖的研究。     

Decreased expression of DMPK: correlation with CTG repeat expansion and fibre type composition in myotonic dystrophy type 1

Abstract Myotonic dystrophy type 1 (DM1) is an autosomal dominant disease caused by a trinucleotide repeatexpansion, cytosine-thymine-guanine (CTG)_n, in the 3′ untranslated region of a gene encoding the myotonic dystrophy protein kinase (DMPK). To correlate CTG expansion and protein expression, we studied muscle specimens from 16 adult DM1 patients using three anti-DMPK antibodies for immunoblotting. We estimated the amount of the full-length DMPK (85 kDa) in muscle biopsies from normal controls and from DM1 patients carrying different (CTG)_n expansions. We found that DMPK concentration was decreased to about 50% in DM patients’ muscles; the protein decrease did not seem correlated with the CTG repeat length. However, the fibre type composition in skeletal muscle seemed somehow to affect DMPK decrease, as the lowest level of the enzyme was found in patients with the lowest content of type 1 fibre.