Electrostimulated cell fusion in cell engineering

A survey of studies on reconstructions of animal and plant cells which apply a new physical method--electrostimulated fusion, is presented. Effects of different factors of the medium on the efficiency of electrofusion is discussed. A detailed account is given of the authors' studies on zygotes reconstruction by combined methods of microsurgery and electrostimulated cell fusion. Advantages of the latter as compared to the widely distributed methods of fusion by polyethylenglycol and Sendai virus are considered. This physical method can play an important role in the progress of cellular engineering.     

Hypothesis: cell volume limits cell divisions

Mammalian somatic cells and also cells of the yeast Saccharomyces cerevisiae are capable of undergoing a limited number of divisions. Reaching the division limit is referred to, apparently not very fortunately, as replicative aging. A common feature of S. cerevisiae cells and fibroblasts approaching the limit of cell divisions in vitro is attaining giant volumes. In yeast cells this phenomenon is an inevitable consequence of budding so it is not causally related to aging. Therefore, reaching a critically large cell volume may underlie the limit of cell divisions. A similar phenomenon may limit the number of cell divisions of cultured mammalian cells. The term replicative (generative) aging may be therefore illegitimate.     

Lymphoblastoid cell variant in contact-mediated cell spreading

We have isolated a clone of human lymphoblastoid cells that is capable of undergoing the phenomenon of contact-mediated cell spreading in vitro. We have detected this behavior when using both transmission electron microscopy (TEM), and differential interference contrast microscopy. Upon cell-cell contact, cells become loosely adherent and then begin to extend cellular processes that contact other cells and the substrate. We have also selected a variant clone that has lost the capability for cell spreading. The adhesion-defective variant becomes adhesion-positive and appears morphologically identical with the adhesive cells only in response to specific amino sugars. In the presence of those sugars the adhesion response is correlated with a shift in the apparent molecular weight of an iodinatable component. We propose that contact-mediated cell spreading in lymphoblastoid cells is mediated by a non-transferable cell surface-associated glycoconjugate. The synthesis of that glycoconjugate is defective in the non-adhesive clone, unless the cells are grown in glucosamine or mannosamine.     

Coupling the cell cycle to cell growth

In order to multiply, both prokaryotic and eukaryotic cells go through a series of events that are collectively called the cell cycle. However, DNA replication, mitosis and cell division may also be viewed as having their own, in principle independent, cycles, which are tied together by mechanisms extrinsic to the cell cycle—the checkpoints—that maintain the order of events. We propose that our understanding of cell-cycle regulation is enhanced by viewing each event individually, as an independently regulated process. The nature of the parameters that regulate cell-cycle events is discussed and, in particular, we argue that cell mass is not such a parameter.     

Familial non-syndromic clear cell renal cell carcinoma

The diagnosis of familial non-syndromic clear cell renal cell carcinoma is one of exclusion. In families presenting with clear cell RCC a germline VHL mutation and a constitutional translocation of chromosome 3 must be excluded before familial non-syndromic clear cell RCC can be diagnosed. Large familial non-syndromic clear cell RCC kindreds are uncommon and a predisposing gene has not been identified. However inheritance is autosomal dominant in most cases and age at onset is earlier than in sporadic cases. Recognition and appropriate screening of familial non-syndromic clear cell RCC cases will reduce morbidity and mortality. Large scale collaborative linkage studies may provide a basis for the identification of familial non-syndromic clear cell RCC susceptibility gene(s).     

Uniform straw-like cell architecture for three-dimensional cell–cell communication assay

ABSTRACT

We fabricated uniform straw-like cell architecture with central lumen using a suture thread within 1 h. The architecture consisting of cancer cells and mature adipocyte was used for cell–cell communication assay, although mature adipocyte could not form spontaneous multi-cellular spheroids. Using the system, it is possible to investigate three-dimensional cell–cell communication as an alternative to animal experiments.     

Potassium channels in cell cycle and cell proliferation

Normal cell-cycle progression is a crucial task for every multicellular organism, as it determines body size and shape, tissue renewal and senescence, and is also crucial for reproduction. On the other hand, dysregulation of the cell-cycle progression leading to uncontrolled cell proliferation is the hallmark of cancer. Therefore, it is not surprising that it is a tightly regulated process, with multifaceted and very complex control mechanisms. It is now well established that one of those mechanisms relies on ion channels, and in many cases specifically on potassium channels. Here, we summarize the possible mechanisms underlying the importance of potassium channels in cell-cycle control and briefly review some of the identified channels that illustrate the multiple ways in which this group of proteins can influence cell proliferation and modulate cell-cycle progression.     

Space and time in the plant cell wall: relationships between cell type, cell wall rheology and cell function

BACKGROUND: The biomechanical behaviour of plant cells depends upon the material properties of their cell walls and, in many cases, it is necessary that these properties are quite specific. Additionally, physiological regulation may require that target cells responding to hormonal signals or environmental factors are able to modulate these characteristics. ARGUMENT: This paper uses a rheological analysis of creep of elongating sunflower (Helianthus annuus) sunflower hypocotyls to demonstrate that the mechanical behaviour of plant cell walls is complex and involves multiple layered processes that can be distinguished from one another by the time-scale over which they lead to a change in tissue dimensions, their sensitivity to pH and temperature, and their responses to changes in spatial arrangement of the cell wall brought about by treatment with high M(r) PEG. Furthermore, it appears possible to regulate individual rheological processes, with limited effect on others, in order to modulate growth without affecting tissue structural integrity. It is proposed that control of the water content of the cell wall and therefore the space between cell wall polymers may be one mechanism by which differential regulation of cell wall biomechanical properties is achieved. This hypothesis is supported by evidence showing that enzyme extracts from growing tissues can cause swelling in cell wall fragments in suspension. IMPLICATIONS: The physiological implications of this complexity are then considered for growing tissues, stomatal guard cells and abscission cells. It is noted that, in each circumstance, a different combination of mechanical properties is required and that differential regulation of properties affecting behaviour over different time-scales is often necessary.     

Tumor cell "dead or alive": caspase and survivin regulate cell death, cell cycle and cell survival

Cell death and cell cycle progression are two sides of the same coin, and these two different phenomenons are regulated moderately to maintain the cellular homeostasis. Tumor is one of the disease states produced as a result of the disintegrated regulation and is characterized as cells showing an irreversible progression of cell cycle and a resistance to cell death signaling. Several investigations have been performed for the understanding of cell death or cell cycle, and cell death research has remarkably progressed in these 10 years. Caspase is a nomenclature referring to ICE/CED-3 cysteine proteinase family and plays a central role during cell death. Recently, several investigations raised some possible hypotheses that caspase is also involved in cell cycle regulation. In this issue, therefore, we review the molecular basis of cell death and cell cycle regulated by caspase in tumor, especially hepatocellular carcinoma cells.     

Review of the effects of cytochalasin B on cell division, cell movemnts, cell exchanges, and cell morphology

Cytochalasin B is known to induce quiescence in cells. We present here a comprehensive view dealing with the effects of cytochalasin B on cell division, movements, exchanges and morphology. The controversial mode of action of the drug is also considered.     

Cellular kinetics,cell cycles and cell killing

Summary Techniques available for the calculation of the time variation of the number of viable mammaliar cells in a cell population are reviewed. Events in the course of the cell's growth may include one or more exposures to ionizing radiations or other cytotoxic agents. The dependence of cell killing upon the cell's position in the cell cycle is emphasized, and a unified model for calculation of cell kinetics and cell survival is discussed. For a cell population not limited in growth by contact inhibition or by nutritional factors, experimental data agree with predictions of the model.The possibility of utilizing the model to arrive at optimum treatment schedules for the management of some malignant diseases is discussed. The conclusion drawn is that the state of knowledge with respect to cellular events in solid tumors is such as to leave most such applications in the realm of speculation.This work was supported by the National Institutes of Health, United States Public Health Service, under Grants CA 5008 and CA 4542.     

Olfactory cell cultures on ensheathing cell monolayers

Olfactory neurons dissociated from the olfactory mucosa of 4–5-week-oldSprague - Dawley rats are plated on either monolayers of ensheathingcells or cortical astrocytes. It is found that the ensheathingcells support a slightly higher percentage of neurite-bearingolfactory neurons than the astrocytes. Scanning electron microscopyshows that some of the cytoplasmic extensions of the ensheathingcells are closely associated with the olfactory axons whileothers appear to ensheath them. Olfactory neurons grown on uncoated,poly-L-lysine or laminin-coated glass coverslips in the presenceof medium conditioned by ensheathing cells fail to grow neurites,suggesting that interaction between membrane molecules, andnot trophic factors, may be required for neurite growth. However,it is unlikely that these membrane molecules are Ll and N-cadherinbecause immunohistochemical staining shows that only a smallproportion of the cultured ensheathing cells express Ll (9%)and N-cadherin (24%).     

Molecular live cell bioimaging in stem cell research

Functional heterogeneity within stem and progenitor cells has been shown to influence cell fate decisions. Similarly, intracellular signaling activated by external stimuli is highly heterogeneous and its spatiotemporal activity is linked to future cell behavior. To quantify these heterogeneous states and link them to future cell fates, it is important to observe cell populations continuously with single cell resolution. Live cell imaging in combination with fluorescent biosensors for signaling activity serves as a powerful tool to study cellular and molecular heterogeneity and the long-term biological effects of signaling. Here, we describe these methodologies, their advantages over classical approaches, and we illustrate how they could be applied to improve our understanding of the importance of heterogeneous cellular and molecular responses to external signaling cues.     

10种常见甲藻细胞体积与细胞碳、氮含量的关系

选择10种常见甲藻,通过构建相应细胞几何模拟图形从而计算了每种甲藻细胞的体积,利用元素分析仪测定了每种甲藻的单个细胞碳、氮含量,并分析了细胞体积与细胞碳、氮含量之间的关系。结果表明,10种常见甲藻的细胞体积差异显著,最小仅为2.97×10² μm³(卡特双甲藻),最大可达到4.50×10⁴ μm³(红色赤潮藻),相差2个数量级;单个细胞碳、氮含量变化范围分别为54.50-2238.00 pg/个和11.42-482.28 pg/个,均相差40多倍。细胞体积与单个细胞碳、氮含量存在极显著的正相关线性关系(P<0.0001)。     

T cell growth factors from adult T cell leukemia virus-transformed cell lines

Some characteristics of T cell growth factors derived from adult T cell leukemia virus (ATLV)-transformed cell lines, MT 1 and MT 2 were analyzed. MT 1 cells release significant interleukin 2 (IL 2) activity into the culture medium, which showed the same elution pattern of gel filtration and isoelectric focusing of IL 2 from lectin-stimulated normal human lymphocytes. This activity was also detected in the cell extract of MT 1. In contrast, MT 2 cell line did not produce IL 2 activity, but non-IL 2 type growth factor was observed. The significance of these factors from MT cell lines is discussed from the viewpoint of 'autokine' in ATLV-transformed cells.     

Lipid peroxidation: control of cell proliferation, cell differentiation and cell death

In recent years, it has become evident that lipid peroxidation is not only a mechanism for deterioration of alimentary oils and fats, but can occur even in living cells, both in pathological and physiological conditions. Through its aldehydic products, it can regulate several cellular processes, as proliferation, differentiation and apoptosis of normal and neoplastic cells. In this review we describe some recent findings obtained in these fields.     

Parvovirus infection-induced cell death and cell cycle arrest

The cytopathic effects induced during parvovirus infection have been widely documented. Parvovirus infection-induced cell death is often directly associated with disease outcomes (e.g., anemia resulting from loss of erythroid progenitors during parvovirus B19 infection). Apoptosis is the major form of cell death induced by parvovirus infection. However, nonapoptotic cell death, namely necrosis, has also been reported during infection of the minute virus of mice, parvovirus H-1 and bovine parvovirus. Recent studies have revealed multiple mechanisms underlying the cell death during parvovirus infection. These mechanisms vary in different parvoviruses, although the large nonstructural protein (NS)1 and the small NS proteins (e.g., the 11 kDa of parvovirus B19), as well as replication of the viral genome, are responsible for causing infection-induced cell death. Cell cycle arrest is also common, and contributes to the cytopathic effects induced during parvovirus infection. While viral NS proteins have been indicated to induce cell cycle arrest, increasing evidence suggests that a cellular DNA damage response triggered by an invading single-stranded parvoviral genome is the major inducer of cell cycle arrest in parvovirus-infected cells. Apparently, in response to infection, cell death and cell cycle arrest of parvovirus-infected cells are beneficial to the viral cell lifecycle (e.g., viral DNA replication and virus egress). In this article, we will discuss recent advances in the understanding of the mechanisms underlying parvovirus infection-induced cell death and cell cycle arrest.     

High density cell culture by membrane-based cell recycle

Enhancement of productivity of a bioprocess necessitates continuous operation of bioreactors with high biomass concentrations than are possible in conventional batch, fedbatch or continuous modes of culture. Membrane-based cell recycle has been effectively used to maintain high cell concentrations in bioreactors. This review compares membranebased cell recycle operation with other such high density cell culture systems as immobilized cell reactors and reactors with cell recycle by centrifugation or gravity sedimentation. A theoretical of production of primary and secondary metabolites in membrane-based recycle systems is presented. Operation of this type of system is discussed with examples from aerobic and anaerobic fermentations.     

Preformed cell structure and cell heredity

This review will first recall the phenomena of “cortical inheritance” observed and genetically demonstrated in Paramecium 40 years ago, and later in other ciliates (Tetrahymena, Oxytricha, Paraurostyla), and will analyze the deduced concept of “cytotaxis” or “structural memory.” The significance of these phenomena, all related (but not strictly restricted) to the properties of ciliary basal bodies and their mode of duplication, will be interpreted in the light of present knowledge on the mechanism and control of basal body/centriole duplication. Then other phenomena described in a variety of organisms will be analyzed or mentioned which show the relevance of the concept of cytotaxis to other cellular processes, mainly (1) cytoskeleton assembly and organization with examples on ciliates, trypanosome, mammalian cells and plants, and (2) transmission of polarities with examples on yeast, trypanosome and metazoa. Finally, I will discuss some aspects of this particular type of non-DNA inheritance: (1) why so few documented examples if structural memory is a basic parameter in cell heredity, and (2) how are these phenomena (which all rely on protein/protein interactions, and imply a formatting role of preexisting proteinic complexes on neo-formed proteins and their assembly) related to prions?Key words: Paramecium, basal-body, centriole, basal-body duplication, cell polarity, structural inheritance, cytotaxis, cell memory, epigenetics