爪蟾脊索细胞的决定

在两栖类,关于脊索对邻近组织的作用有大量的研究工作,但是,相反,关于邻近组织对脊索的影响过去几乎没有任何报道。因此,本工作企图通过外植的方法,研究脊索在早期发育是是如何决定的,是否也受邻近细胞的影响。结果发现,脊索的决定是一个渐进的过程,并提供了研究邻近组织影响的线索。     

邻近组织对爪蟾脊索决定和分化的影响

影响爪蟾脊索决定和分化的因素,过去未见报道。本文采用体外共同培养的方法检测了肌节和神经上皮在脊索决定和分化中的作用。结果指出,脊索与两侧肌节共同培养,肌节的量为脊索的决定和分化提供了足够的条件,一侧肌节的量满足不了使所有脊索进行决定和分化的条件,在少数例子里甚至分化不出脊索。在神经上皮的包裹中,部份脊索细胞向肌细胞分化,单独与脊索接触也不利于脊索的正常分化。讨论了中轴器官之间在决定和分化中错综复杂的关系。     

CORTICAL GRANULES PERSISTING IN GERM CELLS OF XENOPUS LAEVIS AFTER THE CLEAVAGE STAGES

Cortical granules were demonstrated, in two successive Epon sections (0.7 μm thick) stained with PAS reagent and the triple staining method respectively, to persist beyond the cleavage stages of development to the tadpole stages in Xenopus laevis. They were also examined by electron microscope. The granules which are similar both cytochemically and ultrastructurally to the cortical granules of the unfertilized eggs were observed not only in germ cells, pPGCs and PGCs, but also in somatic cells at all the stages examined. An ultrastructural similarity between the granules found in the PGCs at the tadpole stages and chromatoid body was discussed.     

CELL CONTACT REFORMATION OF DISSOCIATED CELLS FROM EMBRYONIC CELLS OF STRONGYLOCENTROTUS PURPURATUS

Disaggregated single cells from the gastrula of Strongylocentrotus purpuratus were studied as they reaggregated and reformed quasi-normal embryos. In this investigation emphasis was placed on the structural events involved during the reformation of cell contacts vis-a-vis cell migration. The early cell contacts are non-junctional cell appositions, which are characterized by non-parallel apposing membranes. Between post-migratory epithelial cells, there is a shift from non-parallel to parallel apposing membranes. These cell appositions are found between the overlapping lamellapodia along the apical margins of the epithelial cells during blastocoel enlargement. Incipient continuous junctions are formed by the deposition of an electron dense material in the intermembrane space. As the junction develops, electron dense plaques form in the cytoplasm immediately subjacent to the junction and septa form between the apposing membranes.     

异型一氧化氮合酶在爪蛙鼻粘膜中的分布

用还原型辅酶Ⅱ黄递酶组织化学和一氧化氮合酶（ＮＯＳ）免疫细胞化学技术研究了成年爪蛙（Ｘｅｎｏｐｕｓｌａｅｖｉｓ）鼻粘膜ＮＯＳ的阳性结构。嗅上皮中嗅感觉神经元和支持细胞,以及固有层中的神经束、血管和粘膜下腺均呈还原型辅酶Ⅱ黄递酶阳性染色。在嗅上皮中,未见Ⅰ型或Ⅱ型ＮＯＳ抗体免疫反应阳性结构,但鼻内侧窦和内侧窦口顶嗅上皮中的嗅感觉神经元见有Ⅲ型ＮＯＳ强免疫反应。在固有层中,Ⅰ型或Ⅲ型ＮＯＳ免疫反应性存在于神经束和血管中,未见于粘膜下腺的腺泡中。结果表明,不同异型的ＮＯＳ存在于爪蛙鼻粘膜中,提示一氧化氮可能参与爪蛙的化学感觉活动。     

KINETIC ANALYSIS OF ENTIRE OOGENESIS IN XENOPUS LAEVIS

In our breeding conditions (without artificial hormonal stimulation) two years after metamorphosis are necessary for a Xenopus laevis female to produce mature oocytes. Four periods of different growth rates can be distinguished into this first wave of oogenesis: 1) oocytes reach 120 μm in diameter (early stage I according to D umont (5)) in a few weeks after metamorphosis; 2) growth slows down and the size of 250–300 μm (late stage I) is obtained 6–7 months later; 3) a rapid growth resumes during vitellogenesis (stages II, III and IV) and a 1,000–1,100 μm diameter is reached in 2–3 months; 4) the last period spans for a year and the oocyte grows up to 1,200 μm. This phase covers many physiological changes and it should be critical to size carefully the oocytes for biochemical investigations and comparisons.
At last most of the oocytes in a young female do not proceed through this entire oogenesis, they are stopped at the end of the second growth phase (about 250 μm in diameter).     

SCANNING ELECTRON MICROSCOPICAL APPEARANCE OF CELLS FROM XENOPUS LAEVIS EMBRYOS OF DIFFERENT STAGES

The scanning electron microscopical appearances of cells isolated from different regions of Xenopus laevis embryos of different stages, and cultured in vitro have been compared. Blastula inner ectoderm cells initially show filopodia, then become flattened onto the substrate and then form pseudopodia. Blastula outer ectoderm cells are initially similar, but do not form pseudopodia. Most of the ectoderm cells from gastrulae and neurulae are featureless. Endoderm cells from blastulae do not initially form filopodia, but later form pseudopodia. Most of the endoderm cells from gastrulae and neurulae show neither filopodia nor pseudopodia, but in the gastrula some elongated, cylindrical cells are observed. Thus cells change their appearance after the three hour culture period; cells from different regions of embryos of the same stage show different appearances in vitro ; and cells from equivalent regions of embryos of different stages show different behaviours in vitro.     

爪蟾胚胎脊髓胆碱能神经元上两类非去极化激活的钙通道

用膜片箝方法,在标定的爪蟾胚胎脊髓胆碱能神经细胞膜上记录钙离子单通道电流。结果显示,在静息膜电位时钙通道即有开放活动。根据通道的电导及动力学等特性,我们将其分为两种类型:NS 型钙通道,斜率电导7.5pS,静息膜电位时平均开放时间0.58ms,其活动受牵张膜片的影响;NL 型钙通道,斜率电导16.7pS,静息膜电位时二级平均开放时间分别是2ms 和19.3ms。鉴于它们在膜静息以及负电位相的显著活动,我们推测这两类钙通道可能参与神经元静息膜电位时钙依赖的细胞活动过程。     

CYCLIC SURFACE CHANGES IN THE NON-NUCLEATE EGG FRAGMENT OF XENOPUS LAEVIS

Fertilized uncleaved eggs of Xenopus laevis were divided into nucleate and non-nucleate egg fragments. Both fragments, together with the whole egg of the same batch, were observed by time-lapse cinematography.
Two kinds of cyclic surface changes, (1) rounding-up and relaxing movements and (2) surface contraction waves, accompanying each cleavage in the whole eggs and the nucleate fragments, were also observed even in the non-nucleate fragments although they do not cleave.
Cleavage intervals of the whole egg and the nucleate fragment were nearly equal, but the rounding-up intervals of the non-nucleate fragment were slightly but definitely longer than the cleavage intervals of the nucleate fragment and the whole egg.     

INITIATION OF RIBOSOMAL RNA SYNTHESIS AND CELL DIVISION IN XENOPUS LAEVIS EMBRYOS

Isolated cells from animal or vegetal pole regions of Xenopus blastulae were cultured, and the timings of rRNA synthesis and cell division were determined. rRNA synthesis was measured by the incorporation of (³H)methionine into rRNA, and cell division was studied by the decrease in cell size and rRNA content. Nucleoli in these cells were also examined. It was found that these animal and vegetal cells continue to divide under the present conditions in the same temporal pattern as that of intraembryonic cells, and that rRNA synthesis begins soon after the cells have undergone the division which probably corresponds to the 15th division following fertilization. At this time, the rRNA content and concentration of the animal and vegetal cells are significantly different. These results seem to support the view that cell division is involved in some way in the mechanism determining the timing of rRNA synthesis in early embryonic development.     

移植非洲爪蟾胚胎细胞核引起花背蟾蜍成熟卵单性发育的研究

将非洲爪蟾胚胎细胞核移入花背蟾蜍成熟未受精卵后,得到了发育至各期的胚胎。对发育不同的时期的胚胎,进行了乳酸脱氢酶同工酶谱及染色体组型分析,结果一显示其均与受体一致。根据实验分析认为,非洲爪蟾的胚胎细胞进入花背蟾蜍成熟卵后,引起的是花背蟾蜍的单性发育。     

CHANGES IN SUSCEPTIBILITY OF CHICK EMBRYONIC BLOOD CELLS TO NEWCASTLE DISEASE VIRUS

To analyse the age-dependent changes in susceptibility of chick embryonic cells to viral infection, observations were made on the blood cells after the inoculation of Newcastle disease virus. A lethal dose of Sato strain of Newcastle disease virus was introduced into chick embryos via injection of inoculum into the blood vessel and allantoic sac. Observations of blood cells by immunofluorescent technique revealed two types of cells, susceptible and resistant to the virus infection. Erythroblasts of both primitive and definitive lines, embryonic thromboblasts and thrombocytes were of the former type and mid- and late-polychromatic erythrocytes and mature ones were of the latter. Erythroblasts gradually decrease in their viral susceptibility as they differentiate into polychromatic erythrocytes and finally become resistant to the virus at the mid-polychromatic erythrocyte stage or later. Thromboblasts, on the other hand, retain high susceptibility to the virus throughout the course of their differentiation to mature thrombocytes. The change in the viral susceptibility of erythroid cells with differentiation is discussed in relation to the structural and functional alterations during the cell specialization.     

用DNA酶切小分子片段在非洲爪蟾卵提取物中实现非细胞体系核装配

用质粒ｐＢＲ３２２的ＤＮＡ酶切片段,长度分别为７５０、３７５和１８６ｂｐ作为外源ＤＮＡ在非洲爪蟾 卵提取物中实现了非细胞体系的核装配（核重建）。将分离纯化得到的 ＰＢＲ３２２ ＤＮＡ酶切后经低熔 点琼脂糖回收ＤＮＡ片段,长度为７５０、３７５和１８６ｂｐ,分别加入到爪蟾卵提取物再生系统中温育, 经ＤＡＰＩ染色、孚尔根染色及电子显微镜观察发现能装配大量的重建核。显微分光光度法研究表 明,ＤＮＡ片段在诱导形成重建核的过程中发生了明显的凝集－会凝集变化。α－３２Ｐ－ｄＣＴＰ掺入重建核 的液闪计数结果表明,ＤＮＡ酶切小分子片段诱导形成的重建核具有较高的ＤＮＡ复制活性,而且复 制活性在一定范围内与加入的ＤＮＡ片段长度呈正相关。实验结果表明,非细胞体系中诱导的核重 建不仅与外源ＤＮＡ的种类无关,与外源ＤＮＡ的长度也没有关系。     

MITOCHONDRIA IN LIVING CELLS: AN ANALYSIS OF MOVEMENTS

Time-lapse cinephotomicrography of mouse embryonic fibroblasts before and shortly after perfusion of tissue cultures reveals that the elongation of mitochondria caused by coenzyme A results from the terminal association of many shorter rods into a smaller number of long filaments. These are not permanent associations, but they reflect an exaggeration of the cohesive tendency of mitochondria, which in untreated cells is counterbalanced by frequent disjoinings and breakings of the anastomotic network. Our own observations and a survey of the literature suggest that elongate mitochondria with rapid movement and high metabolic activity tend to accompany proliferation in tissue cultures, and that mitotic inhibition of cultured cells may go together with short, slow mitochondria of low metabolic activity. The movement of mitochondria may be both active, reflecting metabolic exchanges with the cytoplasm, and passive, the result of hyaloplasmic currents.     

CHANGES IN THE MELANOPHOROTROPIC FUNCTION OF THE PITUITARY GLAND ACCOMPANYING BLINDNESS IN XENOPUS LAEVIS DAUDIN

A number of cases of blindness appeared among a group of cultured Xenopus laevis. The blind toads lacked eyeballs and optic nerves and were consistently dark in color. Similar anatomical changes in the head and pigmentation were produced experimentally by removing the eyeballs of tadpoles or young adult toads. The dark pigmentation of blind Xenopus: was shown to be due to the continuous release of MSH from the pars intermedia of the pituitary, since hypophysectomy led to the complete blanching of the dermal and epidermal melanophores. MSH activity in the pars intermedia of blind toads was extremely high in comparison with that of normal animals. No special difference with respect to the general growth and behaviour was found between normal and blind Xenopus, which suggests that the pituitary functions other than that of the pars intermedia are not affected by the state of the optic nerves. These observations suggest that the retrogressive degeneration of the optic nerves exerts a profound effect on the secretory activity of the pars intermedia via the hypothalamic controlling center.     

利用腺病毒DNA与爪蟾卵提取物在非细胞体系中重构细胞核(简报)

1983年,Lohka和Masui首先报道,用精子染色质与卵提取物一起温育,可以组装成具有典型结构的细胞核。这种核不仅具有合成DNA的能力,而且还能进入M期。同年,