Herpetomonas roitmani (Fiorini et al., 1989) N. Comb.: A Trypanosomatid with a Bacterium-like Endosymbiont in the Cytoplasm

The trypanosomatid previously described as Crithidia roitmani is characterized here at the ultrastructural and biochemical levels. The data indicates that the parasite belongs to the Herpetomonas genus, and we therefore suggest the flagellate to be denominated as Herpetomonas roitmani n. comb. Cladistic analysis of isoenzyme data generated by eight different enzymes showed that the parasite presented a distinct banding pattern and could be grouped with some Herpetomonas spp., but not with Crithidia spp., used as reference strains. Accordingly, when the parasites were grown for longer periods in Roitman's defined medium, expontaneous differentiation from promastigotes to opisthomastigotes (typical of the Herpetomonas genus) occurred. Transmission electron microscopy revealed the presence of bacterium-like endosymbionts in the cytoplasm of all evolutive forms of the parasite. All morphological alterations characteristic of endosymbiont-bearing trypanosomatids could be observed.     

Effect of Differentiation and Cell Density on Glycosphingolipid Class and Molecular Species Composition of Mouse Neuroblastoma NB2a Cells

The effects of cell density and retinoic acid-induced differentiation on the class and molecular species composition of mouse neuroblastoma NB2a cell glycosphingolipids were examined under conditions where the period of culture was controlled. The total amount of neutral glycosphingolipids per cell decreased both with differentiation and as the cells became confluent. The relative amount of the neutral glycosphingolipid classes was not affected by differentiation, whereas there were small but significant changes in the relative amount of the neutral glycosphingolipid classes as the cells became confluent. The total amount of the gangliosides was unaffected by either differentiation or cell density, but there were significant changes in the ganglioside class composition as a result of both cell density and differentiation, and the effects were additive. The molecular species of all the major neutral glycosphingolipid and ganglioside classes were essentially identical, and were altered only slightly by either differentiation or cell density.     

Nutritional Requirements of Blastocrithidia culicis,a Trypanosomatid with an Endosymbiont1

ABSTRACT. The symbiont-containing Blastocrithidia culicis from Aedes vexans, unlike most lower trypanosomatids cultivated in defined media, require only three amino acids: methionine, histidine, and arginine; only three vitamins: thiamin, nicotinamide, and riboflavin; and neither heme nor purine. The bacterium-like endosymbiont presumably provides the trypanosomatid's other essential nutrients.     

Biochemical and ultrastructural changes in Herpetomonas roitmani related to the energy metabolism

Herpetomonas roitmani, a non-pathogenic trypanosomatid was grown in chemically defined media either containing proline or glucose as carbon source. Using transmission electron microscopy we observed that cells grown in the presence of proline present more lipid inclusions, and a larger mitochondrion with more cristae and higher activity of succinate cytochrome c reductase. On the other hand, cells grown with glucose as carbon source had more glycosomes, which were preferentially located close to the bacterium endosymbiont, and a much higher activity of hexokinase, a typical glycosome marker. Three-dimensional reconstruction and morphometrical analysis confirm these observations. The number of promastigotes of H. roitmani increased in the presence of proline. Taken together these results indicate that the growth conditions markedly influenced the ultrastructure and the metabolism of H. roitmani.     

miRNA与细胞分化的研究进展

microRNA(miRNA)是一类长度为22nt的内源性的参与转录后调节的单链非编码小RNA。近年来的研究表明,miRNA在基因表达调控方面具有广泛和普遍的作用,参与了生物体发生发育、细胞增殖、细胞分化等生物学过程,尤其是其在干细胞的自我更新与多向分化的调节作用日益受到关注。我们查阅近年有关文献,介绍了miRNA的生成、作用机制、研究方法,论述及其对真核生物细胞分化的调控作用。     

维甲酸对人神经母细胞瘤SK—N—SH细胞形态结构和分化标志物表达的影响

目的：观察维甲酸对人神经母细胞瘤SK-N-SH细胞形态与超微结构及其相关标志物表达的影响,以鉴定其对神经母细胞瘤细胞终末分化的诱导作用。方法：1μmol／L维甲酸处理SK—N—SH细胞,光镜、电镜和免疫细胞化学检测研究SK—N—SH细胞处理前后细胞形态、超微结构变化和神经元相关标志物的表达变化。结果：光镜与电镜观察结果显示,SK—N—SH细胞经1μmol／LRA处理后,细胞形态和超微结构产生了细胞呈极性状、伸出多个轴突树突状突起、细胞逐渐变小变圆并融合在一起形成类似神经节样结构、细胞表面微绒毛减少、核仁变少变小、常染色质增多、细胞器丰富发达等显著变化;免疫细胞化学检测显示经RA处理后SK-N-SH细胞NSE、MAP2、Synaptophysin的表达较对照组细胞明显加强。结论：维甲酸能改变SK—N—SH细胞形态和超微结构恶性表型特征,并促进与神经细胞相关的终末分化指标的表达,从而对人神经母细胞瘤细胞的终末分化具有显著的诱导作用。     

The Differentiation of Herpetomonas megaseliae: Ultrastructural Observations*

Ultrastructure of both undifferentiated (promastigote and paramastigote) and differentiated (opisthomastigote) forms of Herpetomonas megaseliae is described. There is a posterior migration of the kinetoplast at the end of the exponential growth phase. The posterior extension of the flagellar pocket precedes migration of the kinetoplast. Opisthomastigotes have an electron-translucent mitochondrial matrix in comparison with undifferentiated forms. The Golgi body changes from a stack of flattened sacs to an aggregation of vesicles. Several structures previously reported from Trypanosomatidae, e.g. subpellicular organelles, pellicular microtubules, membrane whorls, stored metabolic products, surface blebs, and an intraflagellar body are also present in H. megaseliae.     

Changes in the DNA,RNA and Protein Contents During the Root-Tip Cell Differentiation of Triticum aestivum

One to two cm long root tips of Triticum aestivum L., after three days' germination at 25 ℃, each were cut into three regions--the meristem region, elongation region and mature region. The cells in different regions were stained with Hochest 33258, Pymnin G and FITC respectively. Nuclear DNA was measured by micmfluorometry with VIDAS digital image analysis system. The relative contents of RNA and protein in the cells were measured with a MPV-Ⅲ microspectrofluorometer. It was shown that the nuclear DNA content increased during root tip cell differentiation, being maximum in the mature region. The relative content of RNA was maximum in the meristem region, but decreased continuously during the growth of tissue. The relative content of protein was maximum in the elongation region, but minimum in the meristem region. The relationships among DNA, RNA, protein and cell differentiation were discussed.     

Effect of Platelet-Activating Factor on the Process of Cellular Differentiation of Herpetomonas muscarum muscarum

ABSTRACT. The effects of platelet-activating factor (PAF), at doses ranging from 10⁻⁶ M to 10⁻¹⁰ M, on cell growth and on cell differentiation of Herpetomonas muscarum muscarum were investigated. Cell differentiation was evaluated by both light and electron microscopy. At the concentrations used, PAF did not interfere with the protozoan growth. However, parasites grown in the presence of PAF (10⁻⁶ M) were significantly more differentiated than those grown in the absence of PAF, since the first day of culture. On the first two days of culture, PAF doses ranging from 10⁻¹⁰ M to 10⁻⁷ M, did not significantly interfere with the differentiation of these parasites, although after the third day of culture, all PAF doses used significantly increased the protozoan differentiation. Specific PAF receptor antagonists totally abrogated (WEB 2086 and WEB 2170)or significantly decreased (BN 52021) PAF effect on cell differentiation. These findings indicate PAF triggers the process of cell differentiation in Herpetomonas muscarum muscarum and suggest these parasites have receptors for PAF.     

Auxin and Kinetin Induced Changes of Callus Cell Wall Composition of Abutilon avicennae Gaertn

In a previous report we have shown that the arrangement of callus cell wail fibrils of Abutilon avicennae could be induced to change under IAA (2 ppm) and kinetin (10 ppm) treatments. Kinetin at this concentration was shown to be able to induce callus cell differentiation and form tracheary elements by changing the orientation of the wall fibrils. It was thus assumed that the hormonal induction of cellular differentiation and structual change of the cell wall may possibly be accompanied by the simultaneous changes of chemical composition of the wall. Attempt was therefore made to investigate if such changes do occur in vitro under the influence of phytohormones. Suspension cell-culture of Abutilon avicennae was used in this experiment to study the hormonal effect on the incorporation of H3-glucose into the cell wall polysaccharides. Analysis of neutral sugars of the cell wall following IAA (2ppm) and kinetin (10ppm) treatments was carried out with a gas chromatography. The results obtained in this experiment are shown in tables 1-2 and figures 1, It was found that the auxin was capable of promoting the synthesis of all neutral sugars, among which the glucose and the maunose in particular, increased tremendously. When H3-glucose was added to the culture medium, IAA was found to enhance the incorporation of the isotopes into the matrix polysaccharides (hemiceUulose and pectin). The result demonstrates clearly that the primary function of IAA is to stimulate the synthesis of hemicellulose composition and, as a consequence, the cell wall retained at the primary growth stage. Kinetin, on the other hand, showed an inhibitory effect on most of the neutral sugars except glucose and mannose. It appeared to have a striking inhibitory action on the synthesis of arabinose and rhanmose (a special composition of pectic substance). It also limited the incorporation of H3-glucose into the pectic substance. It is, therefore, suggested that the action of kinetin may mainly be inhibitory on the synthesis of pectic composition. The decreased rate of pectin synthesis would implicate that the cell wall has been advan ced into the phase of secondary growth. The results presented here agree fairly well with our connotation that there is a parallel relationship between cellular morphology and biochemical characteristics during cell wall differentiation and growth.     

The Root Cap: Cell Dynamics, Cell Differentiation and Cap Function

The root cap is a universal feature of angiosperm, gymnosperm, and pteridophyte roots. Besides providing protection against abrasive damage to the root tip, the root cap is also involved in the simultaneous perception of a number of signals – pressure, moisture, gravity, and perhaps others – that modulate growth in the main body of the root. These signals, which originate in the external environment, are transduced by the cap and are then transported from the cap to the root. Root gravitropism is one much studied response to an external signal. In the present paper, consideration is given to the structure of the root cap and, in particular, to how the meristematic initial cells of both the central cap columella and the lateral portion of the cap which surrounds the columella are organized in relation to the production of new cells. The subsequent differentiation and development of these cells is associated with their displacement through the cap and their eventual release, as border cells, from the cap periphery. Mutations, particularly in Arabidopsis, are increasingly playing a part in defining not only the pattern of genetic activity within different cells of the cap but also in revealing how the corresponding wild-type proteins relate to the range of functions of the cap. Notable in this respect have been analyses of the early events of root gravitropism. The ability to image auxin and auxin permeases within the cap and elsewhere in the root has also extended our understanding of this growth response. Images of auxin distribution may, in addition, help extend ideas concerning the positional controls of cell division and cell differentiation within the cap. However, firm information relating to these controls is scarce, though there are intriguing suggestions of some kind of physiological link between the border cells surrounding the cap and mitotic activity in the cap meristem. Open questions concern the structure and functional interrelationships between the root and the cap which surmounts it, and also the means by which the cap transduces the environmental signals that are of critical importance for the growth of the individual roots, and collectively for the shaping of the root system. Current address (Peter W. Barlow): School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, UK     

二甲双胍调控糖尿病大鼠骨髓间充质干细胞的增殖和分化

虽然二甲双胍广泛用于治疗2型糖尿病,但是其对骨骼的潜在影响知之甚少。因此,本研究评估了二甲双胍对培养的大鼠骨髓间充质干细胞(MSCs)和脂肪细胞两者的分化以及增殖的影响。首先随机组形成对照实验,其中对照组为在不经二甲双胍处理培养基中培养MSCs细胞21 d,而二甲双胍组则在用100μmol/L二甲双胍处理培养基中培养MSCs 21 d。结果表明,二甲双胍增强了大鼠MSCs的成骨细胞分化细胞中ALP的活性,抑制了培养中MSCs脂肪形成分化的过程,但是增强了MSCs细胞的增殖能力。     

Transformations of the Cell Center during Cell Differentiation

A question was posed as to how the multicomponent and polyfunctional organelle dynamically changes during metazoan ontogenesis. The centrosome structure is gradually formed and its functions are switched on during early embryogenesis, one of which is the cell center formation. During cell differentiation, the condition of the cell center and surrounding structures may be different: first, the cell center is quite distinct; second, the cell center is absent due to redistribution of the microtubule organizing centers; third, the cell center disappears due to reversible or irreversible inactivation of the centrosome and other centers of microtubule organization. The assembly of the Golgi complex does not depend directly to the cell center presence. In some cell types, the Golgi complex is topologically associated with the cell center, while in others it exists as individual dictyosomes despite the cell center presence. In some other cell types, the common Golgi complex is assembled without the cell center, but in the presence of microtubules that are formed by noncentrosome centers of microtubule organization. In still others, degradation of both the cell center and the common Golgi complex takes place in the case of centrosome inactivation.     

5－氮－2＇－脱氧胞苷（5－aza－CdR）对HL－60细胞分化和DNA甲基化酶的影响

以５－氮－２＇－脱氧胞苷（５－ａｚａ－ＣｄＲ）为诱导物,在０．５μｍｏｌ／Ｌ的最佳浓度下,可诱导ＨＬ－６０细胞分化达１５％左右。同时,用［￣３Ｈ］－ｍｅｔｈｙｌ－ｓ－ａｄｅｎｏｓｙｌｍｅｔｈｉｏｎｉｎｅ（￣３Ｈ－ＳＡＭ）为底物,通过同位素参入法,测定了不同浓度诱导物对ＨＬ－６０细胞ＤＮＡ甲基化酶活力的影响,发现在最佳诱导物浓度下,可使ＨＬ－６０细胞ＤＮＡ甲基化酶活力明显下降,此外,也比较了不同分化水平的ＨＬ－６０细胞中具有不同甲基化水平的ＤＮＡ在体外接受甲基的能力,从而证明５－ａｚａ－ＣｄＲ诱导ＨＬ－６０细胞分化与其ＤＮＡ甲基化状态密切相关。     

阿拉伯半乳糖蛋白及其在植物细胞分化中的作用

阿拉伯半乳糖蛋白（ａｒａｂｉｎｏｇａｌａｃｔａｎ－ｐｒｏｔｅｉｎｓ,以下简称ＡＧＰｓ）是广泛存在于高等动植物的一种糖蛋白。本文就其化学组成、特性、合成、代谢和其在植物细胞分化中的某些作用的研究进展作了介绍。     

低氧、低氧诱导因子-1和白血病细胞分化

低氧诱导因子-1(HIF-1)是细胞适应低氧反应的主要转录因子,由氧敏感的HIF-1α和组成性表达的HIF-1β组成.系列研究表明,低氧是肿瘤的重要微环境.相应地,HIF-1在实体瘤的发展和转移过程中发挥重要作用.本实验室研究显示,低氧通过HIF-1的转录非依赖功能,即与造血细胞分化相关的转录因子C/EBPα和Runx1/AML1等相互作用,并增加其转录活性,诱导急性髓细胞性白血病细胞分化.本文就低氧和HIF-1在白血病细胞分化中的作用作一综述.     

Platelet-activating factor (PAF) activates casein kinase 2 in the protozoan parasite Herpetomonas muscarum muscarum

Herpetomonas muscarum muscarum is a flagellate parasite of the family Trypanosomatidae, whose cell differentiation can be triggered by the lipid mediator, PAF. In this study we demonstrate for the first time that PAF effect relies on the activation of casein kinase 2 (CK2). The classical antagonist of PAF receptor, WEB 2086, abrogated PAF-enhanced CK2 activity. CK2 activation by PAF was also inhibited when parasite extracts were assayed in the presence of modulators of PKC, MAPK, and both Ser/Thr and Tyr phosphatases. Finally, a cell permeable inhibitor of CK2 (DRB) suppressed PAF-induced cell differentiation in a dose-dependent manner.