Longitudinal zonation pattern in Arabidopsis root tip defined by a multiple structural change algorithm.

Background and Aims The Arabidopsis thaliana root is a key experimental system in developmental biology. Despite its importance, we are still lacking an objective and broadly applicable approach for identification of number and position of developmental domains or zones along the longitudinal axis of the root apex or boundaries between them, which is essential for understanding the mechanisms underlying cell proliferation, elongation and differentiation dynamics during root development. Methods We used a statistics approach, the multiple structural change algorithm (MSC), for estimating the number and position of developmental transitions in the growing portion of the root apex. Once the positions of the transitions between domains and zones were determined, linear models were used to estimate the critical size of dividing cells (LcritD) and other parameters. Key Results The MSC approach enabled identification of three discrete regions in the growing parts of the root that correspond to the proliferation domain (PD), the transition domain (TD) and the elongation zone (EZ). Simultaneous application of the MSC approach and G2-to-M transition (CycB1;1DB:GFP) and endoreduplication (pCCS52A1:GUS) molecular markers confirmed the presence and position of the TD. We also found that the MADS-box gene XAANTAL1 (XAL1) is required for the wild-type (wt) PD increase in length during the first 2 weeks of growth. Contrary to wt, in the xal1 loss-of-function mutant the increase and acceleration of root growth were not detected. We also found alterations in LcritD in xal1 compared with wt, which was associated with longer cell cycle duration in the mutant. Conclusions The MSC approach is a useful, objective and versatile tool for identification of the PD, TD and EZ and boundaries between them in the root apices and can be used for the phenotyping of different genetic backgrounds, experimental treatments or developmental changes within a genotype. The tool is publicly available at www.ibiologia.com.mx/MSC_analysis.

Niche separation in bacterial communities and activities in porewater, loosely attached, and firmly attached fractions in permeable surface sediments.

Heterotrophic microbes are central to organic matter degradation and transformation in marine sediments. Currently, most investigations of benthic microbiomes do not differentiate between processes in the porewater and on the grains and, hence, only show a generalized picture of the community. This limits our understanding of the structure and functions of sediment microbiomes. To address this problem, we fractionated sandy surface sediment microbial communities from a coastal site in Isfjorden, Svalbard, into cells associated with the porewater, loosely attached to grains, and firmly attached to grains; we found dissimilar bacterial communities and metabolic activities in these fractions. Most (84%-89%) of the cells were firmly attached, and this fraction comprised more anaerobes, such as sulfate reducers, than the other fractions. The porewater and loosely attached fractions (3% and 8%-13% of cells, respectively) had more aerobic heterotrophs. These two fractions generally showed a higher frequency of dividing cells, polysaccharide (laminarin) hydrolysis rates, and per-cell O2 consumption than the firmly attached cells. Thus, the different fractions occupy distinct niches within surface sediments: the firmly attached fraction is potentially made of cells colonizing areas on the grain that are protected from abrasion, but might be more diffusion-limited for organic matter and electron acceptors. In contrast, the porewater and loosely attached fractions are less resource-limited and have faster growth. Their cell numbers are kept low possibly through abrasion and exposure to grazers. Differences in community composition and activity of these cell fractions point to their distinct roles and contributions to carbon cycling within surface sediments.

How many cell types form the epithelial lining of the human uterine tubes? Revision of the histological nomenclature of the human tubal epithelium.

INTRODUCTION: Many widely used international histological textbooks claim that the epithelium of the human uterine tube consists of two, three, and, eventually, four types of cells. Most discrepancies among these textbooks relate to debates regarding the presence or absence of basal cells, whether the peg/intercalary cells and secretory cells are the same or distinct cell populations, and if the epithelium contains a population of immunologically active cells (T- and B-lymphocytes, NK cells, macrophages and dendritic cells) or dispersed endocrine cells. METHODS: Uterine tubes were obtained from 22 women (average age: 46.73 y) undergoing gynecological surgery. The women were in fertile age, mostly in the middle of the menstrual cycle (ovulation phase). Tissue samples were processed for immunohistochemistry using primary antibodies against proliferation markers (Ki67 and PCNA), immune system cells (CD1a, CD3, CD4, CD8, CD20, CD45RO, CD56, CD68, granzyme B and S100) and disperse endocrine cells (chromogranin A and synaptophysin). RESULTS: Most of the mature tubal epithelial cells, ciliated cells, and secretory cells were mitotically active (PCNA+), a population of basal undifferentiated cells was not identified. The dividing cells had a narrow-shaped nucleus (Ki67 positive). These cells were morphologically identical to - by the terminology mentioned - intercalary cells, assuming they represented actually dividing cells (epitheliocytus tubarius mitoticus). The tubal "basal cells" displayed small, hyperchromatic nuclei and very pale cytoplasm (clear cytoplasmic halo). They were located in the epithelium adjacent to the basement membrane, were non-mitotically active and their immunophenotype corresponded to intraepithelial regulatory T-lymphocytes (CD3+, CD8+, CD45RO+, CD4-, CD20-, CD56- and granzyme B-). Intraepithelial B-lymphocytes were only rarely identified. Intraepithelial NK cells, dendritic cells, macrophages and dispersed endocrine cells were not identified. CONCLUSIONS: We recommend replacing the term "epitheliocytus tubarius basalis" in the Terminologia Histologica with the term "lymphocytus T intraepithelialis tubarius", which represents intraepithelial regulatory T-cells (CD8+, CD45RO+) of the uterine tube. Additionally, we propose that intercalary/peg cells are actively dividing cells, instead of effete or degenerating cells. Finally, the histological nomenclature should be corrected in a way that peg/intercalary cells are not considered synonymous terms for secretory cells.

At the Crossroads Between Neurodegeneration and Cancer: A Review of Overlapping Biology and Its Implications.

BACKGROUND: A growing body of epidemiologic evidence suggests that neurodegenerative diseases occur less frequently in cancer survivors, and vice versa. While unusual, this inverse comorbidity is biologically plausible and could be explained, in part, by the evolutionary tradeoffs made by neurons and cycling cells to optimize the performance of their very different functions. The two cell types utilize the same proteins and pathways in different, and sometimes opposite, ways. However, cancer and neurodegeneration also share many pathophysiological features. OBJECTIVE: In this review, we compare three overlapping aspects of neurodegeneration and cancer. METHOD: First, we contrast the priorities and tradeoffs of dividing cells and neurons and how these manifest in disease. Second, we consider the hallmarks of biological aging that underlie both neurodegeneration and cancer. Finally, we utilize information from genetic databases to outline specific genes and pathways common to both diseases. CONCLUSION: We argue that a detailed understanding of the biologic and genetic relationships between cancer and neurodegeneration can guide future efforts in designing disease-modifying therapeutic interventions. Lastly, strategies that target aging may prevent or delay both conditions.

Strategies for In Vivo Genome Editing in Nondividing Cells.

Programmable nucleases, including zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), and clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated 9 (Cas9), have enhanced our ability to edit genomes by the sequence-specific generation of double-strand breaks (DSBs) with subsequent homology-directed repair (HDR) of the DSB. However, the efficiency of the HDR pathway is limited in nondividing cells, which encompass most of the cells in the body. Therefore, the HDR-mediated genome-editing approach has limited in vivo applicability. Here, we discuss a mutation type-oriented viewpoint of strategies devised over the past few years to circumvent this problem, along with their possible applications and limitations.

Visualizing the Functional Heterogeneity of Muscle Stem Cells.

Skeletal muscle stem cells are satellite cells that play crucial roles in tissue repair and regeneration after muscle injury. Accumulating evidence indicates that satellite cells are genetically and functionally heterogeneous, even within the same muscle. A small population of satellite cells possesses "stemness" and exhibits the remarkable ability to regenerate through robust self-renewal when transplanted into a regenerating muscle niche. In contrast, not all satellite cells self-renew. For example, some cells are committed myogenic progenitors that immediately undergo myogenic differentiation with minimal cell division after activation. Recent studies illuminate the cellular and molecular characteristics of the functional heterogeneity among satellite cells. To evaluate heterogeneity and stem cell dynamics, here we describe methods to conduct a clonal analysis of satellite cells and to visualize a slowly dividing cell population.

Image-based focused counting of dividing cells for non-invasive monitoring of regenerative medicine products.

Despite the growing numbers of successful applications in regenerative medicine, biotechnologies for evaluating the quality of cells remain limited. To evaluate the cultured cells non-invasively, image-based cellular assessment method holds great promise. However, although there are various image-processing algorithms, very few studies have focused to prove the effectiveness of phase contrast images with risk assessment example that reflects actual difficulties in regenerative medicine products. In this study, we developed a simple image-processing method to recognize the number of dividing cells in time-course phase-contrast microscopic images, and applied this method to assess the irregular proliferation behavior in normal cells. Practically, as a model, rapid proliferating human fibrosarcoma cells were mixed in normal human fibroblasts in the same culture dish, and their sarcoma existence was evaluated. As a result, the existence of sarcoma population in normal cell sample could be feasibly detected within earliest period of cell culture by their irregular rise of accumulated counts of dividing cells. Our image-processing technique also illustrates the technical effectiveness of combining intra-frame and inter-frame image processing to accurately count only the dividing cells. Our concept of focused counting of dividing cells shows a successful example of image-based analysis to quickly and non-invasively monitor the regular state of regenerative medicine products.

MEASUREMENT OF IN SITU SPECIFIC GROWTH RATES OF MICROCYSTIS (CYANOBACTERIA) FROM THE FREQUENCY OF DIVIDING CELLS(1).

Diel changes in the frequency of dividing cells (FDC) of three Microcystis species were investigated in a small eutrophic pond from July to October 2005. The representative species was M. aeruginosa (Kütz.) Kütz., constituting 57%-86% of the Microcystis population throughout the study period, and the remainder were M. viridis (A. Braun) Lemmerm. and M. wesenbergii (Komárek) Komárek. The FDC of M. aeruginosa and M. wesenbergii increased in the daytime and fell in the nighttime in July and August, but this regular variation was not observed in September or October. The in situ specific growth rates of Microcystis species were estimated based on the assumption that the specific growth rate can be given as an absolute value of the derivative of FDC with respect to time. The calculated values were similar among species-0.15-0.38 · d(-1) for M. aeruginosa, 0.14-0.63 · d(-1) for M. viridis, and 0.18-0.61 · d(-1) for M. wesenbergii. The specific growth rates in July and August slightly exceeded those in September and October. The analysis of the in situ specific growth rate of Microcystis indicated that recruitment of the benthic population or morphological change, rather than massive growth, was at least partly responsible for the dominance of M. aeruginosa in the study pond.