东亚飞蝗Locusta migratoria manilensis（Mey．）膝下器中具橛感器的附属细胞和附属结构的超微结构

东亚飞蝗膝下器的具橛感器主要由三类细胞组成．即：感觉细胞、感橛细胞和冠细胞。感觉细胞为具橛感器的主要结构和功能细胞,其超微结构已在其他的文章中描述。感橛细胞是具橛感器的主要支持细胞,从近端到远端依次与神经胶质细胞、感觉细胞的远端树突部分和感觉纤毛部以及顶端细胞外结构——冠、冠细胞直接接触．感橛细胞内最明显的结构为感概,另外,感橛细胞质被高度“空化”。冠细胞紧密包围着感橛细胞和冠,冠细胞中含有大量的纵行微管．并将整个具橛感器连接到体壁上。     

Possible involvement of queuine in regulation of cell proliferation

An increase in cell number is one of the most prominent characteristics of cancer cells. This may be caused by an increase in cell proliferation or decrease in cell death. Queuine is one of the modified base which is found at first anticodon position of specific tRNAs. It is ubiquitously present throughout the living system except mycoplasma and yeast. The tRNAs of Q-family are completely modified to Q-tRNAs in terminally differentiated somatic cells, however hypomodification of Q-tRNA is closely associated with cell proliferation and malignancy. Queuine participates at various cellular functions such as regulation of cell proliferation, cell signaling and alteration in the expression of growth associated proto-oncogenes. Like other proto-oncogenes bcl2 is known to involve in cell survival by inhibiting apoptosis. Queuine or Q-tRNA is suggested to inhibit cell proliferation but the mechanism of regulation of cell proliferation by queuine or Q-tRNA is not well understood. Therefore, in the present study regulation in cell proliferation by queuine in vivo and in vitro as well as the expression of cell death regulatory protein Bcl2 are investigated. For this DLAT cancerous mouse, U87 cell line and HepG2 cell line are treated with different concentrations of queuine and the effect of queuine on cell proliferation and apoptosis are studied. The results indicate that queuine down regulates cell proliferation and expression of Bcl2 protein, suggesting that queuine promotes cell death and participates in the regulation of cell proliferation.     

The 'Inka cell' and its associated cells: ultrastructure of the epitracheal glands in the gypsy moth,Lymantria dispar

The epitracheal glands in pharate and young pupae of Lymantria dispar are located at the base of ventrolateral tracheal trunks in the prothoracic and first through eighth abdominal segments. Each gland is composed of four cells the ultrastructure of which is described in this paper. One large cell and one smaller cell have an endocrine function, while a third cell is exocrine. A fourth cell forms a canal running from the exocrine cell into the trachea. The large endocrine cell, but not the smaller endocrine cell has released its secretions in freshly moulted pupae. The exocrine cell is assumed to be involved in the pupal moult events as well. The physiological role of the different cell types is discussed: The large endocrine cell (type I endocrine cell) is supposedly homologous with the 'Inka cell', which produces ecdysis triggering hormone (ETH) and was previously described in Manduca sexta; the functions of the smaller endocrine cell (type II endocrine cell) and the exocrine cell remain unknown.     

Three-Dimensional Numerical Model of Cell Morphology during Migration in Multi-Signaling Substrates

Cell Migration associated with cell shape changes are of central importance in many biological processes ranging from morphogenesis to metastatic cancer cells. Cell movement is a result of cyclic changes of cell morphology due to effective forces on cell body, leading to periodic fluctuations of the cell length and cell membrane area. It is well-known that the cell can be guided by different effective stimuli such as mechanotaxis, thermotaxis, chemotaxis and/or electrotaxis. Regulation of intracellular mechanics and cell’s physical interaction with its substrate rely on control of cell shape during cell migration. In this notion, it is essential to understand how each natural or external stimulus may affect the cell behavior. Therefore, a three-dimensional (3D) computational model is here developed to analyze a free mode of cell shape changes during migration in a multi-signaling micro-environment. This model is based on previous models that are presented by the same authors to study cell migration with a constant spherical cell shape in a multi-signaling substrates and mechanotaxis effect on cell morphology. Using the finite element discrete methodology, the cell is represented by a group of finite elements. The cell motion is modeled by equilibrium of effective forces on cell body such as traction, protrusion, electrostatic and drag forces, where the cell traction force is a function of the cell internal deformations. To study cell behavior in the presence of different stimuli, the model has been employed in different numerical cases. Our findings, which are qualitatively consistent with well-known related experimental observations, indicate that adding a new stimulus to the cell substrate pushes the cell to migrate more directionally in more elongated form towards the more effective stimuli. For instance, the presence of thermotaxis, chemotaxis and electrotaxis can further move the cell centroid towards the corresponding stimulus, respectively, diminishing the mechanotaxis effect. Besides, the stronger stimulus imposes a greater cell elongation and more cell membrane area. The present model not only provides new insights into cell morphology in a multi-signaling micro-environment but also enables us to investigate in more precise way the cell migration in the presence of different stimuli.     

Cell wall analysis

The cell wall is a rigid structure essential for survival of the fungal cell. Because of its absence in mammalian cells, the cell wall is an attractive target for antifungal agents. Thus, for different reasons, it is important to know how the cell wall is synthesized and how different molecules regulate that synthesis. The Schizosaccharomyces pombe cell wall is mainly formed by glucose polysaccharides and some galactomannoproteins. Here, we describe a fast and reliable method to analyze changes in S. pombe cell wall composition by using specific enzymatic degradation and chemical treatment of purified cell walls. This approach provides a powerful means to analyze changes in (1,3)beta-glucan and (1,3)alpha-glucan, two main polysaccharides present in fungal cell walls. Analysis of cell wall polymers will be useful to search for new antifungal drugs that may inhibit cell wall biosynthesis and/or alter cell wall structure.     

Ultrastructure of Male Gametophyte in Wheat II. Formation and Development of Sperm Cell

Ultrastructural events in wheat sperm cell development were examined from the division of generative cell stage to the maturation of sperm cell in pollen grains. The results are smnmarized as follows: 1. The generative cell in forming microspore by mitosis goes through a series of changes including tile displacement and transformation. It finally becomes a spindle-shaped cell getting ready for another mitosis. The generative cell at this stage is naked. it is only surrounded by both membranes of its own and vegetative cell Most part of the generative cell is occupied by the conspicuous elliptical nucleus with highly condensed chromatin. With the exception of ribosomes, the organelles in the thin layer of generativc cell cytoplasm are obviously fewer and smaller than those in the vegetative cytoplasm. The mierotubules may also be seen in the cytoplasm of spindle-shaped generative cell parallel to the long axis of the cell. There is no amyloplast in generative cell. 2. When the generative cell has moved to the position close to the vegetative nucleus again, it begins to divide. The formation of sperm cells as the result of mitosis of generative cell, and the development of sperm cell involves the following main changes. The shape of the sperm cell tranforms from spherical to elliptical, finally it forms an elongated cell with a tail-like structure. At the sametime, the distribution of cytoplasm gradually concentrated at one end of the sperm cell to form the cytoplasmic extension, so that the so called "tail" of the sperm cell is formed. There are more organelles, especially the mitochondria, assembling in this part. The sperm cell just formed after mitosis is naked and the enclosed plasma membrane is discontinuous. The sperm cell membrane is enclosed by vegetative cell membrane, and the double membranes may be completed at a later stage. It is considered that the period which follows is very short, the deposition of wall material, the callose, occurs to fill up continuously the space between two membranes, but soon after this period the cell wall becomes discontinuous and the wall material is obviously decreased. The significance of the position of the generative cell before its mitosis and the morphological changes during the development of the sperm cell are discussed in this paper.     

Coordinating cell polarity and cell cycle progression: what can we learn from flies and worms?

Spatio-temporal coordination of events during cell division is crucial for animal development. In recent years, emerging data have strengthened the notion that tight coupling of cell cycle progression and cell polarity in dividing cells is crucial for asymmetric cell division and ultimately for metazoan development. Although it is acknowledged that such coupling exists, the molecular mechanisms linking the cell cycle and cell polarity machineries are still under investigation. Key cell cycle regulators control cell polarity, and thus influence cell fate determination and/or differentiation, whereas some factors involved in cell polarity regulate cell cycle timing and proliferation potential. The scope of this review is to discuss the data linking cell polarity and cell cycle progression, and the importance of such coupling for asymmetric cell division. Because studies in model organisms such as Caenorhabditis elegans and Drosophila melanogaster have started to reveal the molecular mechanisms of this coordination, we will concentrate on these two systems. We review examples of molecular mechanisms suggesting a coupling between cell polarity and cell cycle progression.     

Density-dependent tumor cell death and reversible cell cycle arrest: mutually exclusive modes of monocyte-mediated growth control

The population development of five human tumor cell lines is examined under the influence of elutriator-prepared human monocytes in a serum-free hormone- and growth factor-supplemented medium. Analysis was performed by electronic counting and sizing of tumor cell nuclei and flow cytometric detection of cell cycle phases. Tumor cell death is triggered at rather low monocyte:tumor cell ratios (1:2 to 1:4) whereas it is strongly reduced at high monocyte densities. Furthermore, it is shown that confluence of the target cell population is a necessary prerequisite for lysis. The data suggest that in monocyte/tumor cell cocultures the decision on target cell lysis is not made by the effector cell, but rather by the target cell and that the criterion for this decision is the target cell's ability or inability to respond to a monocyte challenge by arresting the cell cycle in G1. Interactions between target cells play an important role in determining the result of this decision process. A common basis is suggested for this kind of density-dependent monocyte-triggered lysis and density-dependent cell death in 3T3 cell cultures as described previously.     

Rapid assay for cell age response to radiation by electronic volume flow cell sorting

A new technique is described for measuring cell survival as a function of cell cycle position using flow cytometric cell sorting on the basis of electronic volume signals. The sorting of cells into different cell age compartments is demonstrated for three different cell lines commonly used in radiobiological research. Using flow cytometric DNA content analysis and [3H]thymidine autoradiography of the sorted cell populations, we demonstrate that the resolution of the age compartment separation is as good as or better than that reported for other cell synchronizing techniques. The variation in cell survival as a function of position in the cell cycle after a single dose of radiation as measured by volume cell sorting is similar to that determined by other cell synchrony techniques. This new method has several advantages, including: no treatment of the cells is required, thus, this method is noncytotoxic; no cell cycle progression is needed to obtain different cell age compartments; the cell population can be held in complete growth medium at any desired temperature during sorting; and a complete radiation age-response assay can be plated in 2 h. The application of this method to problems in radiobiology and chemotherapy is discussed, along with some of the technical limitations.     

Cell cycle transformation in 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 centers of microtubule organization; third, the cell center disappears due to reversible or irreversible inactivation of the centrosome and other centers of microtubule organization. The assembly of the common Golgi complex is not directed directly to the cell center presence. In some cell types, the Golgi complex is topologically associated with the cell center, while in others it is represented by 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.     

Noninvasive diagnosis of a single cell with a probe beam

It is important to distinguish a living/dead cell in cell culture, especially in the regenerate medicine field including cell therapy, since those cells are usually in short supply and consequently the ex vivo culture process should be operated strictly. Conventional methods for distinguishing a living from a dead cell usually require labeling with a dye, which spoils the culture of the cell. Here we show a simple noninvasive method for diagnosing a dead or alive cell with a probe beam. If a cell is alive, the active transport of materials across the cell membrane causes a change of concentration gradients, and this change further induces a change of deflection of a probe beam passing through a vicinity of the cell membrane. If a cell is dead, no or little change in deflection of the probe beam is induced because no or little active materials movement across the cell membrane exists. The deflection of the probe beam is monitored, and judgment on whether a cell is dead or alive from the deflection signal agreed with the conventional decision.     

Theoretical analysis of the effect of cell recycling on recombinant cell fermentation processes.

A cell recycle system is studied for two-stage continuous fermentation. Cell recycle around the second stage provides higher cell concentrations than processes without recycle and a longer residence time of the cell, which is necessary for inducible products, especially in recombinant cell fermentation. Residence time distribution of the cell in the fermentor is important for the optimization of inducible products. The residence time distributions are studied for the cases with and without significant cell growth in the second stage. With cell growth in the second stage, three cases are considered. These are the cases of (1) zero residence time for two daughter cells after the cell division, (2) zero residence time of one daughter cell after the cell division and inherited residence time for the other daughter cell from the mother cell after the cell division, and (3) two daughter cells having the residence time of the mother cell after the cell division.     

CELL—CELL CONTACTS ACCELERATE CELL COLONY GROWTH IN SPARSE CULTURES OF CHICK EMBRYO FIBROBLASTS

There is no cell proliferation in very sparcely plated chick embryo cell cultures. Substituting conditioned medium or adding of ethanol-fixed homologous cells to the cultures accelerates cell colony growth. The mechanism for the mitogenic action of fixed cells is considered to be the contact stimulation of cell proliferation, and addition of extra cells to sparse culture is believed to mimic the cell micro-environment existing in subconfluent cultures. The role of diverse cell—cell contacts in cultured cell growth regulation is discussed. The procedure used (addition of ethanol-fixed cells) may improve normal cell cloning techniques.     

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.     

Nanoparticle induced cell magneto-rotation: monitoring morphology, stress and drug sensitivity of a suspended single cancer cell

Single cell analysis has allowed critical discoveries in drug testing, immunobiology and stem cell research. In addition, a change from two to three dimensional growth conditions radically affects cell behavior. This already resulted in new observations on gene expression and communication networks and in better predictions of cell responses to their environment. However, it is still difficult to study the size and shape of single cells that are freely suspended, where morphological changes are highly significant. Described here is a new method for quantitative real time monitoring of cell size and morphology, on single live suspended cancer cells, unconfined in three dimensions. The precision is comparable to that of the best optical microscopes, but, in contrast, there is no need for confining the cell to the imaging plane. The here first introduced cell magnetorotation (CM) method is made possible by nanoparticle induced cell magnetization. By using a rotating magnetic field, the magnetically labeled cell is actively rotated, and the rotational period is measured in real-time. A change in morphology induces a change in the rotational period of the suspended cell (e.g. when the cell gets bigger it rotates slower). The ability to monitor, in real time, cell swelling or death, at the single cell level, is demonstrated. This method could thus be used for multiplexed real time single cell morphology analysis, with implications for drug testing, drug discovery, genomics and three-dimensional culturing.     

Regulation of cell wall biogenesis in Saccharomyces cerevisiae: the cell wall integrity signaling pathway

The yeast cell wall is a strong, but elastic, structure that is essential not only for the maintenance of cell shape and integrity, but also for progression through the cell cycle. During growth and morphogenesis, and in response to environmental challenges, the cell wall is remodeled in a highly regulated and polarized manner, a process that is principally under the control of the cell wall integrity (CWI) signaling pathway. This pathway transmits wall stress signals from the cell surface to the Rho1 GTPase, which mobilizes a physiologic response through a variety of effectors. Activation of CWI signaling regulates the production of various carbohydrate polymers of the cell wall, as well as their polarized delivery to the site of cell wall remodeling. This review article centers on CWI signaling in Saccharomyces cerevisiae through the cell cycle and in response to cell wall stress. The interface of this signaling pathway with other pathways that contribute to the maintenance of cell wall integrity is also discussed.     

Fission Yeast Germinal Center (GC) Kinase Ppk11 Interacts with Pmo25 and Plays an Auxiliary Role in Concert with the Morphogenesis Orb6 Network (MOR) in Cell Morphogenesis

How cell morphology and the cell cycle are coordinately regulated is a fundamental subject in cell biology. In fission yeast, 2 germinal center kinases (GCKs), Sid1 and Nak1, play an essential role in septation/cytokinesis and cell separation/cell polarity control, respectively, as components of the septation initiation network (SIN) and the morphogenesis Orb6 network (MOR). Here we show that a third GCK, Ppk11, is also required for efficient cell separation particularly, at a high temperature. Although Ppk11 is not essential for cell division, this kinase plays an auxiliary role in concert with MOR in cell morphogenesis. Ppk11 physically interacts with the MOR component Pmo25 and is localized to the septum, by which Ppk11 is crucial for Pmo25 targeting/accumulation to the septum. The conserved C-terminal WDF motif of Ppk11 is essential for both septum accumulation of Pmo25 and efficient cell separation. In contrast its kinase activity is required only for cell separation. Thus, both interaction of Ppk11 with Pmo25 and Ppk11 kinase activity are critical for efficient cell separation.     

Multiple signalling pathways establish cell fate and cell number in Drosophila malpighian tubules

A unique cell, the tip mother cell, arises in the primordium of each Drosophila Malpighian tubule by lateral inhibition within a cluster of achaete-expressing cells. This cell maintains achaete expression and divides to produce daughters of equivalent potential, of which only one, the tip cell, adopts the primary fate and continues to express achaete, while in the other, the sibling cell, achaete expression is lost (M. Hoch et al., 1994, Development 120, 3439-3450). In this paper we chart the mechanisms by which achaete expression is differentially maintained in the tip cell lineage to stabilise cell fate. First, wingless is required to maintain the expression of achaete in the tubule primordium so that wingless mutants lack tip cells. Conversely, increasing wingless expression results in the persistence of achaete expression in the cell cluster. Second, Notch signalling is restricted by the asymmetric segregation of Numb, as the tip mother cell divides, so that achaete expression is maintained only in the tip cell. In embryos mutant for Notch tip cells segregate at the expense of sibling cells, whereas in numb neither daughter cell adopts the tip cell fate resulting in tubules with two sibling cells. Conversely, when numb is overexpressed two tip cells segregate and tubules have no sibling cells. Analysis of cell proliferation in the developing tubules of embryos lacking Wingless after the critical period for tip cell allocation reveals an additional requirement for wingless for the promotion of cell division. In contrast, alteration in the expression of numb has no effect on the final tubule cell number.     

Autophagic cell death: Loch Ness monster or endangered species?

The concept of autophagic cell death was first established based on observations of increased autophagic markers in dying cells. The major limitation of such a morphology-based definition of autophagic cell death is that it fails to establish the functional role of autophagy in the cell death process, and thus contributes to the confusion in the literature regarding the role of autophagy in cell death and cell survival. Here we propose to define autophagic cell death as a modality of non-apoptotic or necrotic programmed cell death in which autophagy serves as a cell death mechanism, upon meeting the following set of criteria: (i) cell death occurs without the involvement of apoptosis; (ii) there is an increase of autophagic flux, and not just an increase of the autophagic markers, in the dying cells; and (iii) suppression of autophagy via both pharmacological inhibitors and genetic approaches is able to rescue or prevent cell death. In light of this new definition, we will discuss some of the common problems and difficulties in the study of autophagic cell death and also revisit some well-reported cases of autophagic cell death, aiming to achieve a better understanding of whether autophagy is a real killer, an accomplice or just an innocent bystander in the course of cell death. At present, the physiological relevance of autophagic cell death is mainly observed in lower eukaryotes and invertebrates such as Dictyostelium discoideum and Drosophila melanogaster. We believe that such a clear definition of autophagic cell death will help us study and understand the physiological or pathological relevance of autophagic cell death in mammals.     

Long-term cultivation of in vitro <Emphasis Type="Italic">Apis mellifera</Emphasis> cells by gene transfer of human c-myc proto-oncogene

Establishment of cell lines representative of honeybee character would greatly assist in their analysis. Here, we show that immortalized cell line, designated as MYN9, has been generated from honeybee embryo by the gene transfer of human c-myc proto-oncogene. The morphology of the cell is characteristic of embryonic stem cell, although the cell is stable and does not spontaneously differentiate. Polymerase chain reaction analyses show that the cell is originated from authentic honeybee cell. It is proposed that the integration of human c-myc gene into honeybee precursor populations results in the establishment of stable cell line suitable for cellular and molecular studies.