DYNAMICS OF NERVE CELLS : I. THE TEMPERATURE COEFFICIENT OF THE NEUROGENIC RHYTHM OF THE HEART OF LIMULUS POLYPHEMUS.

In the case of the heart of Limulus polyphemus the same magnitude and variation of the temperature coefficient (Q ₁₀) is obtained from the whole heart as from the ganglion alone. From the magnitude of the temperature coefficients and their variation with changes of temperature we may conclude that the rate of the heart beat is determined by alteration of chemical processes in the ganglion cells.     

SYNTHETIC STRANDS OF CARDIAC MUSCLE : Formation and Ultrastructure

Spontaneously active bundles of cardiac muscle (synthetic strands) were prepared from isolated cells of 11–13-day old embryonic chick hearts which were disaggregated with trypsin. Linear orientation of the cells was obtained by plating them on agar-coated culture dishes in which either grooves were cut in the agar film or a thin line of palladium was deposited over the agar. The influence of cell-to-cell and cell-to-substrate interactions was observed with time lapse cinematography and the formation of the synthetic strand was shown to involve both random and guided cell movements, enlargement of aggregates by accretion and coalescence, and the compact linear arrangement of cells along paths of preferential adhesion. Electron microscope investigations of these strands showed that a dispersed population of heart cells organized into an inner core of muscle cells and an outer sheath of fibroblast-like cells. The muscle cells contained well-developed, but widely spaced myofibrils, a developing sarcoplasmic reticulum associated in part with the myofibrils and in part with the sarcolemma, an abundance of nonmembrane bound ribosomes and glycogen, and a prominent Golgi complex. Numerous specialized contacts were observed between the muscle cells in the strand, e.g., fasciae adherentes, desmosomes, and nexuses. A distinct type of muscle cell characterized by its pale appearance was regularly observed in the strand and was noted to be similar to Purkinje cells described in the adult avian conduction system and in developing chick myocardium. The present findings were compared with other observations of the developing myocardium, in situ, and it was concluded that, by a number or criteria, the muscle cells of the strand were differentiating normally and suitably organized for electrophysiological studies.     

DYNAMICS OF NERVE CELLS : II. THE TEMPERATURE COEFFICIENTS OF CARBON DIOXIDE PRODUCTION BY THE HEART GANGLION OF LIMULUS POLYPHEMUS.

1. It is possible to determine by the colorimetric method the rate of production of carbon dioxide by the cardiac ganglion of Limulus. 2. Carbon dioxide formation in the cardiac ganglion was found to run parallel to the rate of heart beat for different temperatures. 3. The conclusion seems justified that the rate of cardiac rhythm of Limulus depends upon a chemical reaction in the nerve cells of the cardiac ganglion and that this reaction is associated with the production of carbon dioxide since the rate of beat and the rate of CO₂ production are similarly affected by changes in temperature.     

EMBRYO AND ORGAN CULTURES OF THE HORSESHOE CRAB,TACHYPLEUS TRIDENTATUS*

This paper deals with some preliminary technical experiments on cultures of the embryos and organs of Tachypleus tridentatus. In embryo culture, using the embryos at various stages of development, embryonic areas with hardly any yolk remaining in them were cultured in various media and by various methods (Series A); hemispheres of embryos containing the embryonic area (Series B) and whole embryos without egg membranes (Series C) were cultured in sterilized sea water. The suitability of the culture media and methods is described; the medium containing calf serum or 199, and the hanging-drop method were found to be the most appropriate of those used in respective series of experiments. The changes in external and internal structures of the explants from embryos at various developmental stages cultured in various media and by various methods are described; dorsal closure, secretion of inner egg membrane, thickening of the cell layer and the elongation of limb buds were all observed in the Series A experiments. In Series B and C, coelom formation and also normal development of the embryos cultured after the 2nd embryonic moulting were observed. In organ culture, fragments of the embryonic heart were cultured in various media and by various methods. The hanging-drop method resulted in longer survival than the method using agar media.     

中国鲎变形细胞超微结构的进一步观察

中国鲎的变形细胞可在血液中发育成熟,根据其超微结构,可分为原始变形细胞、幼变形细胞和变形细胞三个阶段。 变形细胞受到外环境或内毒素的刺激后,第一型颗粒出现一系列变化,最终把内容物释放到细胞外。与此同时,细胞表面形成若干胞质性突起,边缘带分散断裂,质膜下和胞质性突起中出现微丝。第二型颗粒无变化,提示它们和血液凝胶化过程无直接关系。     

THE ULTRASTRUCTURE OF MAMMALIAN CARDIAC MUSCLE

Papillary muscles of rat and dog hearts were fixed in such a way as to prevent excessive shortening during the procedure. The material was embedded in either araldite or methacrylate and was stained in various ways. The filamentous fine structure of mammalian cardiac muscle is similar to that previously described for striated skeletal muscle. The sarcomeres are composed of a set of thick and thin filaments which interdigitate in the A band proper. The filament ratios and the filamentous array are in accord with those found in skeletal muscle. The functional significance of this twofold array of filaments is not entirely clear. Various other structural aspects of cardiac cells such as surface membranes, mitochondria, nuclei, and cytoplasmic granules are described. The sarcoplasmic reticulum is discussed in detail as are the various structural components forming the intercalated discs. Fairly frequent deep invaginations of the sarcolemma with basement membrane are observed in addition to the intercalated discs. These surface membrane invaginations probably explain the branching appearance of cardiac fibers as seen under the light microscope.     

不同钙离子浓度对鲎腹神经光感受器二种光碰击的影响

在生理盐水中用持续的弱光（６＊１０＾６－９＊１０＾６个光子／ｃｍ＾２）刺激鲎的腹神经光感受器细胞可得到二种类型的碰击,一种称谓“标准光碰击”或“Ｃ２碰击”,它有对称的形状,信号衰退的指０数常数大于０．０１／毫秒。     

中国鲎血细胞原代培养及部分生物学现象观察

中国鲎（Tachypleustridentatus）,隶属于节肢动物门（Arthropoda）、有螯亚门（Chelicerata）、肢口纲（Merostomata）、剑尾目（Xiphosura）、鲎科（Limulidae）,分布于中国、日本和东南亚其他国家。鲎科动物（Horseshoecrab）现有三属四种,自从早古生代奥陶纪出现,至今4亿多年,其形态结构以及生活习性无重大变化。在胚胎发育后期有三叶虫幼体的形态特征,被誉为活化石。在天然免疫、视觉、胚胎发育等许多方面,鲎成为研究者的模式动物。     

中国鲎胚胎血细胞生成的初步电镜观察

人工孵育的鲎胚,以光镜和电镜观察其血细胞发生过程。血细胞包括变形细胞和蓝细胞二系列,均可分为原始、幼稚和成熟三阶段。血细胞生成开始于胚胎的附肢原基形成阶段,变形细胞最早见于胚区,蓝细胞先出现于胚外部分。鲎胚中未发现具备组织结构的造血器官,造血系在结缔组织和血腔中进行。     

TEMPERATURE AND FREQUENCY OF CARDIAC CONTRACTIONS IN EMBRYOS OF LIMULUS

Temperature characteristics for frequency of myogenic heart beat in Limulus embryos, before the onset of nervous control of the heart, were found to be 11,500; 16,400; 20,000; 25,500. The two first values are the best established. The different values pertain to the hearts of different individuals outwardly similar, and to the hearts of single embryos in different parts of the temperature range. These values differ from that known in connection with the control of the heart beat through the cardiac ganglion. The occurrence of critical temperatures, also, is not the same in all embryos. These facts are employed in a discussion of temperature relations in pulsating explants of chick myocardium.     

中国鲎幼体阶段(黄皮鲎)的形态特点

经研究发现,中国鲎幼体阶段（黄皮鲎）生殖盖板中叶不长于侧叶,尾呈三角形,上有一列小刺,腹甲后端尾上有三个棘突,尾两个侧边无小刺,腹甲背面无小刺分布,但其头胸甲和腹甲背面棘突较长,明显呈幼体状,中国鲎的胚后幼体发育从小到大,身体背部颜色处于黑色→土黄色→褐色的一种渐变过程,当中国鲎幼体头胸甲宽度处于10-25cm时,也就是胚后发育的第12至第16次蜕皮期间时,其体色呈土黄色,在粤西、海南、北部湾一带俗称“黄皮鲎”。所以,黄皮鲎为中国鲎一定阶段未成熟的幼体,而不是一个新种或亚种。标本采自广东省湛江市,保存于湛江海洋大学水生生物博物馆。     

A STRAND OF CARDIAC MUSCLE : Its Ultrastructure and the Electrophysiological Implications of Its Geometry

The structure of a small strand of rabbit heart muscle fibers (trabecula carnea), 30–80 µ in diameter, has been examined with light and electron microscopy. By establishing a correlation between the appearance of regions of close fiber contact in light and electron microscopy, the extent and distribution of regions of close apposition of fibers has been evaluated in approximately 200 µ length of a strand. The distribution of possible regions of resistive coupling between fibers has been approximated by a model system of cables. The theoretical linear electrical properties of such a system have been analyzed and the implications of the results of this analysis are discussed. Since this preparation is to be used for correlated studies of the electrical, mechanical, and cytochemical properties of cardiac muscle, a comprehensive study of the morphology of this preparation has been made. The muscle fibers in it are distinguished from those of the rabbit papillary muscle, in that they have no triads and have a kind of mitochondrion not found in papillary muscle. No evidence of a transverse tubular system was found, but junctions of cisternae of the sarcoplasmic reticulum and the sarcolemma, peripheral couplings, were present. The electrophysiological implications of the absence of transverse tubules are discussed. The cisternae of the couplings showed periodic tubular extensions toward the sarcolemma. A regularly spaced array of Z line-like material was observed, suggesting a possible mechanism for sarcomere growth.     

IMMUNOHISTOCHEMICAL LOCALIZATION OF CONTRACTILE PROTEINS IN LIMULUS STRIATED MUSCLE

Limulus paramyosin and myosin were localized in the A bands of glycerinated Limulus striated muscle by the indirect horseradish peroxidase-labeled antibody and direct and indirect fluorescent antibody techniques. Localization of each protein in the A band varied with sarcomere length. Antiparamyosin was bound at the lateral margins of the A bands in long (~ 10.0 µ) and intermediate (~ 7.0 µ) length sarcomeres, and also in a thin line in the central A bands of sarcomeres, 7.0–~6.0 µ. Antiparamyosin stained the entire A bands of short sarcomeres (<6.0). Conversely, antimyosin stained the entire A bands of long sarcomeres, showed decreased intensity of central A band staining except for a thin medial line in intermediate length sarcomeres, and was bound only in the lateral A bands of short sarcomeres. These results are consistent with a model in which paramyosin comprises the core of the thick filament and myosin forms a cortex. Differential staining observed using antiparamyosin and antimyosin at various sarcomere lengths and changes in A band lengths reflect the extent of thick-thin filament interaction and conformational change in the thick filament during sarcomeric shortening.     

A MORPHOMETRIC STUDY ON THE NEXUS OF RAT CARDIAC MUSCLE

A morphometric study of the nexus of rat cardiac muscle was carried out. The nexus surface of one intercalated disk of one 15 µm thick fiber is found to range between 47 µm² and 94 µm², the latter value taking into account the maximal underestimation caused by tangential sectioning. Dividing the lower, minimal value by the surface of the observed subunits (90 Å periodicity), one obtains for one intercalated disk 6.7 x 10⁵ subunits, each of them assumed to be permeated by a central pore. These pores are thought to be equivalent to intercellular channels in a recently proposed model. Taking our morphometric and recently reported physiological values, this model is examined for its consistency with a low resistance pathway between cardiac muscle cells.