The effects of modifying RhoA and Rac1 activities on heterotypic contact inhibition of locomotion

Contact inhibition of locomotion (CIL) occurs when a cell ceases moving in the same direction following contact with another cell. Homotypic and heterotypic CIL occur between cells of the same and different types, respectively. Using Abercrombie's confronted explants assay we studied the effect of changing Rac1 or RhoA activities on heterotypic CIL between NIH3T3 and chicken heart fibroblasts. Both dominant active (L61) and dominant negative (N17) Rac1 expressed in NIH3T3 cells resulted in loss of heterotypic CIL. N17Rac1 expression caused RhoA activation. Increasing RhoA activity directly (V14RhoA) or indirectly (downregulation of N-cadherin or p120-catenin) also resulted in loss of CIL. High RhoA activity has been associated with tumour invasion and our results are consistent with loss of heterotypic CIL playing a role.     

Single-section counting error when distinguishing between primordial and early primary follicles in sections of rat ovary of different thickness

The number of primordial follicles within an ovary is frequently determined by counting 5, 7 or 10 microns thick sections and multiplying by the fraction of sections counted and a correction factor to adjust for duplicate counts. The objectives of the present study were: (i) to evaluate the accuracy of the correction factor developed by Abercrombie (1946); (ii) to evaluate the accuracy of the classification of primordial follicles from single tissue sections; and (iii) to determine the incorporation rate of 5-bromo-2-deoxyuridine into primordial follicles. In Expt 1, rat ovaries were sectioned at a thickness of 5, 7 or 10 microns. Primordial follicles were counted and classified across ten adjacent ovarian sections. The percentage of primordial follicles from single sections that were counted twice was 10, 9 and 2% in 5, 7 and 10 microns sections, respectively. This was lower than predicted by Abercrombie's method. The major error in counting from single sections was classification of early primary follicles as primordial follicles (55, 33 and 3% in 5, 7 and 10 microns sections, respectively). In Expt 2, a mean of 12 +/- 7% of primordial follicles incorporated 5-bromo-2-deoxyuridine after infusion for 7 days (four of seven rats had no labelled primordial follicles). In conclusion: (i) Abercrombie's correction factor should not be used for adjusting counts of follicles; (ii) evaluation of primordial follicles from single sections gives inaccurate counts and incorrect classification is of greater importance than duplicate counting, particularly in thinner sections; (iii) for evaluation of the number of follicles, 10 microns is the optimal thickness; and (iv) primordial follicles incorporated 5-bromo-2-deoxyuridine infrequently.     

A mycoplasma high-affinity transport system and the in vitro invasiveness of mouse sarcoma cells.

FS9 mouse sarcoma cells were previously shown to be highly invasive when confronted with chicken heart fibroblasts using Abercrombie's confronted explant technique. This invasion could be inhibited by addition to the assay of Fab fragments of a monoclonal antibody directed against p37, a protein associated with the surface of FS9 cells. We have cloned and sequenced the gene for p37. We show that it originates from Mycoplasma hyorhinis and that UGA is a tryptophan codon in this organism. We present evidence that the p37 gene is part of an operon encoding two additional proteins which are highly similar to components of the periplasmic binding-protein-dependent transport systems of Gram-negative bacteria, and we suggest that p37 is part of a homologous, high-affinity transport system in M. hyorhinis, a Gram-positive bacterium. We discuss the influence of p37 and M. hyorhinis on contact inhibition of locomotion of mammalian cells.     

Aging in the vestibular nuclear complex of the male golden hamster (Mesocricetus auratus): anatomic and morphometric study

To study the effects of senescence on the vestibular nuclear complex twenty brainstems from male golden hamsters between 3 and 27 months-old were used and the possible variations in the number of neurons, neuronal morphology and nuclear volume were studied. The neuron profiles were drawn with a camera lucida and Abercrombie's method was used to estimate the total number of neurons. The test of Kolmogorov-Smirnov with the correction of Lilliefors was used to evaluate the fit of our data to a normal distribution and a regression analysis was done to decide if the variation of our data with age was statistically significant. The results of the present study are relevant only for male animals and the effect of senescence could be different in female vestibular nuclear complex. Aging affects the volume of the superior and lateral vestibular nuclei, as well as the nuclear neuronal diameter of the medial vestibular nucleus, but no significant neuronal loss has been appreciated in vestibular nuclear complex related with age. During the aging process we have observed that the distribution of neurons within the vestibular nuclei of the golden hamster does not show important changes and most of their morphometric parameters do not vary significantly.     

Some mechanisms of lymphoid cell differentiation

Lymphoid cells differentiation is a well coordinated and highly integrated process, which is defined by the interaction of genes and cell signaling pathways of the maturing cell with the microenvironment factors. In the course of such interaction in the maturing cell, new ways of signal transduction appear, and on the basis of such new ways new gene networks are formed, which start to play rapidly, even during the course of the present or following cell specialization stage, the key role in the further cell fate.     

基于微系统技术的细胞微操控、细胞图形化方法及应用

微系统技术给细胞研究提供了一个全新的平台。细胞图形化（Cell Patterning）技术作为全新的细胞培养方式,在细胞研究中发挥重要作用。本文介绍了目前应用于细胞图形化的主要技术,包括光刻（Photolithography）、软光刻（Soft lithography）、模板辅助（Stencil-assisted patterning）等方法,并阐述了利用细胞图形化技术的在基础生物学、组织工程以及基于细胞的生物传感器等方面的主要应用。     

Circadian and infradian aspects of the cell cycle: from past to future

A review of some aspects of circadian and infradian rhythms of the cell cycle is given. The background is that the research of the last decade has given entirely new insights into the cell cycle as a dynamic process which occurs in waves. After some short historical notes on the development of methodology for study of cell kinetics, it is reviewed how the strong variability of this function was recognized from the 1960's. This again led to an increasing understanding of the rhythmic pattern of cell renewal in various tissues of the body. Conventional methods for studying cell population kinetics gave general insights into both circadian and infradian rhythms, but were hampered by several shortcomings. The techniques were time consuming, and usually one and only one parameter could be studied at a time. However, this general knowledge both had a strong impact on the understanding of cell kinetics and provided a basis for designing cancer chemotherapy. Today we are facing a new area in the study of cell population kinetics. New, rapid and automated methods for multiparameter studies of both cell kinetics and other biological properties of cell populations have given entirely new possibilities for cell kinetic research. Methods, mainly connected to analytical cytology, can discriminate subpopulations with varying kinetic properties, and also enable monitoring of cell proliferation in normal and malignant tissues of patients. Chronobiology has had a strong impact on the understanding of cell population kinetics in the body. In the light of the new developments in the fields of growth factors and their regulatory influences on the cell cycle, important and fundamental aspects of biological rhythms are now being elucidated.     

Insect cell culture and applications to research and pest management

Building on earlier research, insect cell culture began with the successful establishment of one cell line from pupal ovarian tissue. The field has grown to the extent that now over 500 insect cell lines have been established from many insect species representing numerous insect orders and from several different tissue sources. These cell lines are used as research tools in virology, in studies of signaling mechanisms to study insect immunity, hemocyte migration, and to test hypotheses about gene expression, and in screening programs designed to discover new insecticide chemistries. Virology research is revealing fundamentally new information on virus/host cell interactions. Studies in gene expression are uncovering signal transduction pathways that are new to insect science. Research is leading to the development of high-speed screening technologies that are essential in the search for new insect pest management tools. A few insect cell lines are, in routine industrial processes, designed to produce proteins of biomedical significance. Both primary cell cultures and established lines are used in basic biological studies to reveal how insect cells work. This review is designed to briefly cover the history of insect cell culture, recount some recent advances in the field, and offer a vision of the future of insect cell culture.     

Kinetics of microbial cell growth

As a rate equation of microbial cell growth, the Monod equation is widely used. However, this equation cannot fully correspond to real courses of microbial cell growth in many batch cultivations. Especially, predicted values based on this equation do not agree with observed values in many continuous cultivations. In this paper, which introduces new concepts of critical concentration and coefficient of consumption activity, the growth rate equation which corresponds to the whole period including lag period is newly derived and characteristics of microbial cell growth in batch cultivation are clarified. Further, applying the new rate equation to continuous cultivation, a general equation with which to calculate cell concentration is derived and characteristics of microbial cell growth in continuous cultivation are clarified. The calculated values of cell concentration based on the new theory showed quite good agreement with the observed values in both batch and continuous cultivation.     

Staphylococcal surface display in combinatorial protein engineering and epitope mapping of antibodies

The field of combinatorial protein engineering for generation of new affinity proteins started in the mid 80s by the development of phage display. Although phage display is a prime example of a simple yet highly efficient method, manifested by still being the standard technique 25 years later, new alternative technologies are available today. One of the more successful new display technologies is cell display. Here we review the field of cell display for directed evolution purposes, with focus on a recently developed method employing Gram-positive staphylococci as display host. Patents on the most commonly used cell display systems and on different modifications as well as specific applications of these systems are also included. General strategies for selection of new affinity proteins from cell-displayed libraries are discussed, with detailed examples mainly from studies on the staphylococcal display system. In addition, strategies for characterization of recombinant proteins on the staphylococcal cell surface, with an emphasis on an approach for epitope mapping of antibodies, are included.     

Spatial and temporal localization of cell wall associated pili in Enterococcus faecalis

Enterococcus faecalis virulence requires cell wall-associated proteins, including the sortase-assembled endocarditis and biofilm associated pilus (Ebp), important for biofilm formation in vitro and in vivo. The current paradigm for sortase-assembled pilus biogenesis in Gram-positive bacteria is that sortases attach substrates to lipid II peptidoglycan (PG) precursors, prior to their incorporation into the growing cell wall. Contrary to prevailing dogma, by following the distribution of Ebp and PG throughout the E. faecalis cell cycle, we found that cell surface Ebp do not co-localize with newly synthesized PG. Instead, surface-exposed Ebp are localized to the older cell hemisphere and excluded from sites of new PG synthesis at the septum. Moreover, Ebp deposition on the younger hemisphere of the E. faecalis diplococcus appear as foci adjacent to the nascent septum. We propose a new model whereby sortase substrate deposition can occur on older PG rather than at sites of new cell wall synthesis. Consistent with this model, we demonstrate that sequestering lipid II to block PG synthesis via ramoplanin, does not impact new Ebp deposition at the cell surface. These data support an alternative paradigm for sortase substrate deposition in E. faecalis, in which Ebp are anchored directly onto uncrosslinked cell wall, independent of new PG synthesis.     

Bacterial shape: growing off this mortal coil

Members of the actin-like MreB family of proteins localize as a helical filament in bacteria and are important for determining cylindrical cell shape. Recent results show that new cell wall biosynthesis occurs along a helical track dependent on one of these actin homologs, providing new insights into bacterial cell growth, division and shape.     

Cell cycles and in vitro transdifferentiation and regeneration of isolated, striated muscle of jellyfish

Isolated, mononucleated, cross-striated muscle cells of a medusa can transdifferentiate in vitro to various new cell types and even form a complex regenerate. The transdifferentiation events follow a strict pattern. The first new cell type resembles smooth muscle and is formed without a preceding DNA replication. This cell type behaves like a stem cell and by quantal cell cycles produces all other new cell types. Some preparations develop an inner and an outer layer separated by a basal lamella. Formation of these layers does not depend on DNA replication. When layers do not form, each division results in nerve cells and smooth muscle cells. If separation into layers occurs, then a regenerate will be formed, and in the course of only two cell cycles all necessary cell types to form a functional regenerate will differentiate.     

A role of carbohydrate-carbohydrate interaction in the process of specific cell recognition during embryogenesis and organogenesis: a preliminary note

A possible role of cell surface glycoconjugates in cell recognition has been envisioned based on recognition of carbohydrates by cell surface proteins such as endogenous lectins, glycosyltransferases, and hydrolases (refs. 18-22 in text). A new possibility that a specific carbohydrate at the cell surface could be recognized by the same or similar carbohydrate on the counterpart cell surface is now suggested by specific interaction between Lex and Lex, but not between Lex and sialylated or non-substituted type 2 chain. A new hypothesis is hereby proposed for carbohydrate-carbohydrate interactions as recognition signals during embryogenesis and organogenesis.     

Tetraspanin functions and associated microdomains

Cell-surface proteins of the tetraspanin family are small, and often hidden by a canopy of tall glycoprotein neighbours in the cell membrane. Consequently, tetraspanins have been understudied and underappreciated, despite their presence on nearly all cell and tissue types. Important new genetic evidence has now emerged, and is bolstered by new insights into the cell biology, signalling and biochemistry of tetraspanins. These new findings provide a framework for better understanding of these mysterious molecules in the regulation of cellular processes, from signalling to motility.     

Induction of a new alkaline band at a target position in internodal cells of Chara corallina

Characean cells develop alternating alkaline and acid bands on their surface upon illumination. However, the mechanism of band formation is not fully understood. In the present study, we succeeded in inducing a new alkaline band at an original acid band in internodal cells of Chara corallina. Chloroplasts in an acid band were locally removed by wounding the cell in the absence of the cell turgor pressure. The chloroplast-removed area was observed as a white belt in a green cylindrical internodal cell. This internodal cell developed a new alkaline band on the surface at the chloroplast-removed area. The narrower the chloroplast-removed area, the less significant the extent of OH(-) extrusion. This is the first success in inducing a new alkaline band at a target position in Characeae.     

Dispersed mode of Staphylococcus aureus cell wall synthesis in the absence of the division machinery

We have developed several new fluorescent staining procedures that enabled us to study the synthesis of cell wall material in the spherical Gram-positive bacterium Staphylococcus aureus. The results obtained support previous proposals that these cells synthesize new wall material specifically at cell division sites, in the form of a flat circular plate that is subsequently cleaved and remodelled to produce the new hemispherical poles of the daughter cells. We have shown that formation of the septal peptidoglycan is dependent on the key cell division protein FtsZ, which recruits penicillin-binding protein (PBP) 2. Unexpectedly, in FtsZ-depleted cells, the cell wall synthetic machinery becomes dispersed and new wall material is made in dispersed patches over the entire surface of the cells, which increase in volume by up to eightfold before lysing. The results have implications for understanding the nature of S. aureus morphogenesis and for inhibitors of cell division proteins as drug targets.     

Best practices for naming,receiving, and managing cells in culture

One of the first considerations in using an existing cell line or establishing a new a cell line is the detailed proactive planning of all phases of the cell line management. It is necessary to have a well-trained practitioner in best practices in cell culture who has experience in receiving a new cell line into the laboratory, the correct and appropriate use of a cell line name, the preparation of cell banks, microscopic observation of cells in culture, growth optimization, cell count, cell subcultivation, as well as detailed protocols on how to expand and store cells. Indeed, the practitioner should best manage all activities of cell culture by ensuring that the appropriate certified facilities, equipment, and validated supplies and reagents are in place.     

On a Model of Pattern Regeneration Based on Cell Memory

We present here a new model of the cellular dynamics that enable regeneration of complex biological morphologies. Biological cell structures are considered as an ensemble of mathematical points on the plane. Each cell produces a signal which propagates in space and is received by other cells. The total signal received by each cell forms a signal distribution defined on the cell structure. This distribution characterizes the geometry of the cell structure. If a part of this structure is removed, the remaining cells have two signals. They keep the value of the signal which they had before the amputation (memory), and they receive a new signal produced after the amputation. Regeneration of the cell structure is stimulated by the difference between the old and the new signals. It is stopped when the two signals coincide. The algorithm of regeneration contains certain rules which are essential for its functioning, being the first quantitative model of cellular memory that implements regeneration of complex patterns to a specific target morphology. Correct regeneration depends on the form and the size of the cell structure, as well as on some parameters of regeneration.     

Cell Division, a new open access online forum for and from the cell cycle community

ABSTRACT : Cell Division is a new, open access, peer-reviewed online journal that publishes cutting-edge articles, commentaries and reviews on all exciting aspects of cell cycle control in eukaryotes. A major goal of this new journal is to publish timely and significant studies on the aberrations of the cell cycle network that occur in cancer and other diseases.