横纹肌肌原纤维的第三肌丝──肌联蛋白

实验研究证明,在动物横纹肌肌原纤维中,除包含有粗肌丝、细肌丝外,还有纤肌丝的存在,肌联蛋白（肌巨蛋白）是具有挠性的线状蛋白质,分子量为3000 000,长度约为0.9μm,跨越肌原纤维的M－线和Z－线,形成纤肌丝.其生理功能是在粗肌丝装配中具有分子模板作用,并将粗肌丝稳定于肌原纤维肌小节中央以及可参与肌球蛋白活性的调节.     

鸣鸣蝉（Oncotympana maculaticollis Motsch）发声肌中肌原纤维的双阵列结构及莫发声原初过程的分析

给出了鸣鸣蝉发声肌肌原纤维的双阵列结构,其肌纤维中并存两种不同阵列的“快”和“慢”动肌原纤维（ＦＳＭ和ＳＳＭ）．ＦＳＭ和ＳＳＭ虽然由粗肌丝构成相同的阵列骨架,但细肌丝对粗肌丝的比例（ＲＴＩＦ）不同,分别为３：１和５：１．明显区别于单音调鸣声的蝉类发声肌肌原纤维的ＲＴＩＦ为３：１的单阵列结构,即与鸣鸣蝉变音调声产生的原初机制相适应．     

Myosin light chain kinase expression during smooth muscle development

The expression of smooth muscle myosin light chain kinase (MLCK) was investigated during chicken gizzard development. The molecular weight and the antigenic properties of MLCK did not change during development. The use of anion exchange high performance liquid chromatography (HPLC) enabled us to distinguish between MLCKs from post-hatched and adult chickens. A partial amino acid sequence determination of 4-day-old gizzard MLCK failed to disclose differences in the primary sequences of the two proteins. The results suggest that MLCK has the same primary sequence in all sequences of the two proteins. The results suggest that MLCK has the same primary sequence in all stages of gizzard development, although charge variants due to post-translational modifications may exist.     

Effects of testosterone on a sexually dimorphic frog muscle: Repeated in vivo observations and androgen receptor distribution

In the present study the sexually dimorphic, androgen-sensitive flexor carpi radialis muscle (FCR) in male Xenopus laevis was viewed repeatedly in vivo to assess the influence of testosterone on muscle fiber size over a period of up to 12 weeks. Regions of the muscle innervated by different spinal nerves responded differently to testosterone treatment. Muscle fibers innervated by spinal nerve 2 (SN2) hypertrophied within 7 days in frogs that had been castrated and given testosterone-filled implants. This initial hypertrophy was followed by a return to normal fiber size a week late, after which fiber size slowly increased again. In castrated males with empty implants, muscle fibers innervated by SN2 gradually atrophied. Fibers innervated by spinal nerve 3 (SN3) were not affected by androgen replacement or withdrawal. The sartorius, a control muscle that is neither sexually dimorphic nor particularly androgen sensitive, was also unaffected. The in vivo observations were confirmed by measurements of muscle fiber cross-sectional areas in frozen sections of whole forelimbs. At 8 and 12 weeks after castration, cross-sectional areas of fibers innervated by SN2 were significantly larger in frogs provided with testosterone than in castrates without testosterone. No difference was found in the SN2 region or in the anconeus caput scapulare (triceps), another control muscle. Immunocytochemistry employing an antibody against the androgen receptor (AR) indicated that the receptor is present in myonuclei of all muscles of the forelimb. While no difference in labeling intensity was detected, the number of AR-containing nuclei per muscle fiber cross-section was higher in fibers innervated by SN2 than in those innervated by SN3, and was yet lower in the triceps. This suggests that regulation of androgen sensitivity may occur via muscle fiber. ARs, although an influence of the nerve may also contribute. 1994 John Wiley & Sons, Inc.     

大黄素对豚鼠结肠带平滑肌细胞电和收缩性能的影响

联合应用平滑肌肌力张力测量技术和细胞内微电极记录技术,同步地现测豚鼠结肠带平滑肌自发的肌源性电活动和力学活动,研究了大黄素的药物作用。大黄素能缩短膜电位的波动周期,从而缩短峰电位集簇发放的周期;相应地,可使平滑肌的分节律收缩加快,幅值指数升高。大黄素又能促使细胞膜电位自发的周期性波动的出现,导致峰电位的集簇发放;相应地,可使强直收缩转化为分节律收缩,即促进收缩形式向有利于肠道推进功能的方向转化。以上结果表明,大黄素能有效地提高豚鼠结肠带平滑肌细胞的电兴奋性和收缩功能,并且对其电学和力学活动的影响之间有明确的对应关系。     

人骨骼肌α辅肌动蛋白（α－actinin）的提取及其抗血清的制备和鉴定

本文提取人骨骼肌α辅肌动蛋白（α－ａｃｔｉｎｉｎ）是综合了文献报导有关提取兔肌α－ａｃｔｉｎｉｎ的和提取鸡胗α－ａｃｔｉｎｉｎ的方法,稍加修改而确定的。用Ｈａｓｓｅｌｂａｃｈ－Ｓｃｈｎｅｉｄｅｒ缓冲液提取骨骼肌中的肌球蛋白后,将残余物经硼酸－缓冲液提取、匀浆及高速离心去掉肌动蛋白和肌原纤维的其它成份,上清加硫酸铵至３０％,３５％饱合度所得的沉淀用２２０ｍｍｏｌ／ＬＴｒｉｓ－乙酸溶解、透析、离心后经ＤＥ－５２柱层析可得电泳纯。α－ａｃｔｉｎｉｎ。将人骨骼肌α－ａｃｔｉｎｉｎ纯化制品免疫了三只大耳白纯种家兔,两个多月后,三只兔子都产生免抗人骨骼肌α－ａｃｔｉｎｉｎ的特异抗血清,用双向免疫扩散法和酶联免疫吸附试验（ＥＬＩＳＡ）测定,产生的抗体效价较高,用双扩散法测定效价为１：３２,用ＥＬＩＳＡ测定,用比率法判断结果,效价最高者为１：１００,０００左右,经免疫电镜观察结果证实,上述抗血清可以满足进一步实验要求。     

Mobilization of intracellular calcium in cultured vascular smooth muscle cells by uridine triphosphate and the calcium ionophore A23187

The known action of uridine triphosphate (UTP) to contract some types of vascular smooth muscle, and the present finding that it is more potent than adenosine triphosphate in eliciting an increase in cytosolic Ca²⁺ concentration in aortic smooth muscle, led us to investigate the mode of action of this nucleotide. With this aim, cultured bovine aorta cells were subjected to patch-clamp methodologies under various conditions. Nucleotide-induced variations in cytosolic Ca²⁺ were monitored by using single channel recordings of the high conductance Ca²⁺-activated K⁺ (Maxi-K) channel within on-cell patches as a reporter, and whole-cell currents were measured following perforation of the patch. In cells bathed in Na⁺-saline, UTP (>30 nm) induced an inward current, and both Maxi-K channel activity and unitary current amplitude of the Maxi-K channel transiently increased. Repetitive exposures elicited similar responses when 5 to 10 min wash intervals were allowed between challenges of nucleotide. Oscillations in channel activity, but not oscillation in current amplitude were frequently observed with UTP levels > 0.1 m. Cells bathed in K⁺ saline (150 m) were less sensitive to UTP (5-fold), and did not show an increase in unitary Maxi-K current amplitude. Since the increase in amplitude occurs due to depolarization of the cell membrane, a change in amplitude was not observed in cells previously depolarized with K⁺ saline. The enhancement of Maxi-K channel activity in the presence of UTP was not diminished by Ca²⁺ entry blockers or by removal of extracellular Ca²⁺. However, in the latter case, repetitive responses progressively declined. These observations, as well as data comparing the action of low concentrations of Ca²⁺ ionophores (<5 m) to that of UTP indicate that both agents elevate cytosolic Ca²⁺ by mobilization of this ion from intracellular pools. However, the Ca²⁺ ionophore did not cause membrane depolarization, and thus did not change unitary current amplitude. The effect of UTP on Maxi-K channel activity and current amplitude was blocked by pertussis toxin and by phorbol 12-myristate 13-acetate (PMA), but was not modified by okadaic acid, or by inhibitors of protein kinase C (PKC). Our data support a model in which a pyrimidinergic receptor is coupled to a G protein, and this interaction mediates release of Ca²⁺ from intracellular pools, presumably via the phosphatidyl inositol pathway. This also results in activation of membrane channels that give rise to an inward current and depolarization. Ultimately, smooth muscle contraction ensues. PKC does not appear to be directly involved, even though the UTP response is blocked by low nm levels of PMA. While the latter data implicate PKC in diminishing the UTP response, agents that inhibit either PKC or phosphatase activity did not prevent abolition of UTP responses by PMA, nor did they modify basal channel activity.     

Do independent processes control the activation and inactivation of potassium contracture tension in rat skeletal muscle?

Potassium (K⁺) contracture tension, measured in small bundles of rat soleus muscle fibers during maintained depolarization, increases to a peak value and then decays either to the baseline or to a pedestal level. We have tested the hypothesis that the rise and fall of tension are determined by independent activation and inactivation processes. If the “Independence” hypothesis is correct, tension during the decay of K⁺ contractures should equal tension predicted from the product of the activation and inactivation parameters determined from the same K⁺ contractures. Both the measured and predicted tensions decayed to a pedestal level that was increased in amplitude in the presence of perchlorate ions. However, the measured tensions in normal solutions and in the presence of perchlorate were three to five times smaller than the predicted tensions. This result indicates that the activation and inactivation of processes controlling the rise and decay of K⁺ contracture tension are not independent.     

In situ hybridization and immunocytochemical localization of SERCA2 encoded Ca2+ pump in rabbit heart and stomach

Heart tissue contains large amounts of the protein encoded by the Ca²⁺ pump gene SERCA2. The SERCA2 RNA can be spliced alternatively to produce mRNA encoding the proteins SERCA2a and SERCA2b which differ in their C-terminal sequences. In this study we report the tissue distribution of SERCA2a and SERCA2b isoforms byin situ hybridization to rabbit heart and stomach. The expression of SERCA2 mRNA was high in myocardial cells, being the highest in the atrial region. In contrast, there was more SERCA2 protein in Western blots in ventricles than in atria. Myocardial cells expressed predominantly the mRNA for the isoform SERCA2a. Whereas the stomach smooth muscle and the neuronal plexus expressed SERCA2 at levels much lower than myocardial cells, the expression was very high in the stomach mucosa. Mucosa contained mainly the mRNA for SERCA2b. From immunocytochemistry it was concluded that the anti-heart SR Ca²⁺ pump antibody IID8 reacted much better with heart and surface mucosal cells in the stomach than with the stomach smooth muscle, and that IID8 reactivity was intracellular. In contrast PM4A2B, an antibody against the plasma membrane Ca²⁺ pump, reacted well with heart and stomach smooth muscle, plexus and mucosa, and its localization appeared to be in the plasma membrane. Thus, stomach smooth muscle expressed SERCA2b mRNA and protein at low levels, mucosa expressed SERCA2b mRNA and protein at high levels, atria and ventricle expressed SERCA2a mRNA and protein at high levels, mRNA being more in atria, but protein being more in ventricles.Deceased August 14, 1992     

Expression of connexin43 gap functions between cultured vascular smooth muscle cells is dependent upon phenotype

The smooth muscle cell is the predominant cell type of the arterial media. In the adult vascular system, smooth muscle cells are found primarily in the contractile phenotype, but following injury or during atherosclerotic plaque formation the secretory synthetic phenotype is expressed. Recently it has been shown that gap junction connexin43 messenger RNA levels are six times higher in cultured smooth muscle cells in the synthetic phenotype than in intact aorta. We have modulated rabbit aortic smooth muscle cells in culture between the synthetic phenotype and one resembling the contractile phenotype, and correlated gap junction expression with phenotype. A dual labelling technique with antibodies against smooth muscle myosin and a synthetic peptide constructed to match a portion of the connexin43 gap junction protein was used for these experiments. Gap junctions are numerous between synthetic phenotype cells but few are observed between contractile cells. Rat aortic smooth muscle cells were also cultured and the growth and structure of gap junctions followed in the synthetic phenotype by use of freeze-fracture electron microscopy and immunohistochemical techniques. Junctional plaques are similar in structure to those observed in cardiac muscle, their size and number increasing with time in culture. The increased numbers of gap junctions between synthetic phenotype smooth muscle cells may be important during vessel development, following injury, or in atherosclerotic plaque formation.