Gametic differentiation in Chlamydomonas reinhardtii. I. Production of gametes and their fine structure.

Gametogenesis in Chlamydomonas reinhardtii has been studied in mating-type plus cells utilizing several different culture conditions, all of which are shown to depend on the depletion of nitrogen from the medium, and the fine structure of gametes prepared under these conditions has been compared by using thin sections of fixed materials. We document alterations in ribosome levels, in chromatin morphology, in starch levels, in the organization of chloroplast membranes, and in the appearance of nuclear envelope and endoplasmic reticulum membranes during gametogenesis. We also noted the acquisition of two new organelles: a mating structure (Friedman, L., A. L. Colwin, and L. H. Colwin. 1968. j. cell Sci. 3:115-128; goodenough, U. W., and R. L. Weiss. 1975. J. Cell Biol. 67:623-637), and Golgi-derived vesicles containing a homogeneous material. We chart the time course of these morphological changes during synchronous gametogenesis. We note that many of these changes may represent adjustments to nitrogen starvation rather than direct features of gametic differentiation, and we also document that cells can differentiate so that they survive conditions of nitrogen starvation for many weeks after they become gametes. We conclude that metabolic alterations, the acquisition of mating ability, and the preparation for long-term survival are all elicited in this organism by nitrogen withdrawal, and we discuss how the various structural alterations observed in this study may relate to these three interrelated avenues of cellular differentiation.

Download Full-text

Fine structure of Arthrobacter crystallopoietes during long-term starvation of rod and spherical stage cells

Canadian Journal of Microbiology ◽

10.1139/m73-001 ◽

1973 ◽

Vol 19 (1) ◽

pp. 1-5 ◽

Cited By ~ 9

Author(s):

Charles W. Boylen ◽

Jack L. Pate

Keyword(s):

Electron Microscopy ◽

Cell Wall ◽

Fine Structure ◽

Cell Size ◽

Morphological Changes ◽

Thin Sections ◽

Size And Shape ◽

Arthrobacter Crystallopoietes ◽

Total Starvation

Actively growing spherical and rod-shaped cells of Arthrobacter crystallopoietes were subjected to total starvation in buffer for 8 weeks. At intervals, thin sections of cells were prepared and examined by electron microscopy. Starving cells underwent no morphological changes that would account for their unusual survival capabilities. Cell size and shape remained unaltered. There was no thickening of the cell wall and no development of structures similar to those observed in spores or cysts. As the length of starvation increased, the following changes were observed; glycogen deposits disappeared, the number of ribosome particles decreased, the number of vesicular membranes increased within the cell, and the nucleoplasm expanded in volume to fill the emptying cytoplasm.

Download Full-text

Long-term survival ofLegionella pneumophilaserogroup 1 under low-nutrient conditions and associated morphological changes

FEMS Microbiology Letters ◽

10.1111/j.1574-6968.1992.tb05794.x ◽

1992 ◽

Vol 102 (1) ◽

pp. 45-55 ◽

Cited By ~ 35

Author(s):

Christine Paszko-Kolva ◽

Manouchehr Shahamat ◽

Rita R. Colwell

Keyword(s):

Morphological Changes ◽

Term Survival ◽

Long Term Survival ◽

Nutrient Conditions

Download Full-text

Sex ratio and morphological characteristics of rufous gnateaters, Conopophaga lineata (Aves, Passeriformes) in Atlantic forest fragments

Iheringia Série Zoologia ◽

10.1590/s0073-47212009000100017 ◽

2009 ◽

Vol 99 (1) ◽

pp. 115-119 ◽

Cited By ~ 3

Author(s):

Gisele P. M. Dantas ◽

Fabrício R. Santos ◽

Miguel Ângelo Marini

Keyword(s):

Sex Ratio ◽

Morphological Changes ◽

Anthropogenic Activities ◽

Natural Populations ◽

Morphological Characteristics ◽

Atlantic Rain Forest ◽

Forest Fragments ◽

Natural Habitats ◽

Term Survival

Unequal sex ratios lead to the loss of genetic variability, decreasing the viability of populations in the long term. Anthropogenic activities often disturb the natural habitats and can cause alterations in sex ratio and morphological characteristics of several species. Forest fragmentation is a major conservation concern, so that understanding its effects in natural populations is essential. In this study, we evaluated the sex ratio and the morphological characteristics of Rufous Gnateaters (Conopophaga lineata (Wied, 1831)) in small and large forest fragments in Minas Gerais, Brazil. Birds (n = 89) were sexed by plumage characteristics and molecular markers. The molecular analysis showed that plumage is not a totally reliable method for sexing Rufous Gnateaters. We observed that sex ratio did not differ between large and small forest fragments, but birds in small fragments had larger wings and tarsus. Wing and tarsus changes may affect the movement ability of individuals within and among forest fragments. In conclusion, Rufous Gnateaters have been able to survive in both small and large Atlantic rain forest fragments without altering their sex ratio, but morphological changes can be prejudicial to their long term survival.

Download Full-text

Minimizing Stress Shielding and Cement Damage in Cemented Femoral Component of a Hip Prosthesis through Computational Design Optimization

Advances in Orthopedics ◽

10.1155/2017/8437956 ◽

2017 ◽

Vol 2017 ◽

pp. 1-12 ◽

Cited By ~ 4

Author(s):

Abdellah Ait Moussa ◽

Justin Fischer ◽

Rohan Yadav ◽

Morshed Khandaker

Keyword(s):

Hip Prosthesis ◽

Numerical Technique ◽

Stress Shielding ◽

Computational Design ◽

Functionally Graded ◽

Implant Design ◽

Homogeneous Material ◽

Element Analysis ◽

Term Survival

The average life expectancy of many people undergoing total hip replacement (THR) exceeds twenty-five years and the demand for implants that increase the load-bearing capability of the bone without affecting the short- or long-term stability of the prosthesis is high. Mechanical failure owing to cement damage and stress shielding of the bone are the main factors affecting the long-term survival of cemented hip prostheses and implant design must realistically adjust to balance between these two conflicting effects. In the following analysis we introduce a novel methodology to achieve this objective, the numerical technique combines automatic and realistic modeling of the implant and embedding medium, and finite element analysis to assess the levels of stress shielding and cement damage and, finally, global optimization, using orthogonal arrays and probabilistic restarts, were used. Applications to implants, fabricated using a homogeneous material and a functionally graded material, were presented.

Download Full-text

IMMU-37. DIRECT REPROGRAMMING OF GLIOBLASTOMA TO ANTIGEN PRESENTING-LIKE CELLS BY MASTER REGULATORS PREDICTED FROM AN ARTIFICIAL INTELLIGENCE PLATFORM

Neuro-Oncology ◽

10.1093/neuonc/noaa215.467 ◽

2020 ◽

Vol 22 (Supplement_2) ◽

pp. ii112-ii113

Author(s):

Dan Jin ◽

Mathew Sebastian ◽

Son Le ◽

Dongjiang Chen ◽

Nagheme Thomas ◽

...

Keyword(s):

Artificial Intelligence ◽

Morphological Changes ◽

Antigen Presenting Cells ◽

Term Survival ◽

Powerful Approach ◽

Antigen Presenting ◽

Fate Determinants ◽

Capacity Characteristic

Abstract Glioblastoma (GBM) is the most common and lethal malignant brain cancer in adults. Immunotherapy has emerged as a potentially powerful approach to achieve long-term survival in patients with GBM. Antigen presenting cells (APCs) play a central role in priming cancer-specific immune responses due to their ability to sample and present tumor neoantigens to the immune system. We hypothesis that antigen presenting cells could be induced by transdifferentiated from GBM in-situ so that these locally created APC will find themselves pre-planted in the tumor microenvironment (TME) with full access to tumor neoantigens. Top ten ranked candidate fate determinants for the GBM-DC transdifferentiation were predicted by NETZEN, an integrated deep-learning and gene network-based ranking artificial intelligence (AI) platform for precision medicine. We successfully transdifferentiated the murine GBM cell line GL261 into CD45+ immune cells accompanying morphological changes to less adhering cells by a combination of four factors (PU.1, IRF8, BATF3, ID2). Of these induced CD45 positive cells, a significant fraction also expresses high levels of the myeloid marker CD11b and antigen presenting molecules MHCII and MHCI by flow cytometry, suggesting these induced CD45+ cells are myeloid lineage APCs (iAPC).These iAPC exhibit phagocytic property, tested by incubating pHrodo Red bioparticles conjugated with Zymosan, an antigen found on the surface of fungi. More importantly, these induced iAPC appear to have lost their proliferative capacity characteristic of the parental GBM cells. Total live cell numbers were significantly reduced in 4F-induced culture compared to the EV control. In conclusion, we successfully transdifferentiated mouse GBM cells into APC-like cells based on NETZEN prediction and our work can potentially provide a novel therapeutic approach for developing an in-situ APC vaccine immunotherapy for GBM, and for other cancers.

Download Full-text

Optimized Culture Conditions for Improved Growth and Functional Differentiation of Mouse and Human Colon Organoids

Frontiers in Immunology ◽

10.3389/fimmu.2020.547102 ◽

2021 ◽

Vol 11 ◽

Author(s):

Sarah S. Wilson ◽

Martha Mayo ◽

Terry Melim ◽

Heather Knight ◽

Lori Patnaude ◽

...

Keyword(s):

Epithelial Cell ◽

Current Knowledge ◽

Human Colon ◽

Cell Types ◽

Functional Differentiation ◽

Culture Conditions ◽

Conditioned Media ◽

Term Survival ◽

The Impact

Background & AimsDiligent side-by-side comparisons of how different methodologies affect growth efficiency and quality of intestinal colonoids have not been performed leaving a gap in our current knowledge. Here, we summarize our efforts to optimize culture conditions for improved growth and functional differentiation of mouse and human colon organoids.MethodsMouse and human colon organoids were grown in four different media. Media-dependent long-term growth was measured by quantifying surviving organoids via imaging and a cell viability readout over five passages. The impact of diverse media on differentiation was assessed by quantifying the number of epithelial cell types using markers for enterocytes, stem cells, Goblet cells, and enteroendocrine cells by qPCR and histology upon removal of growth factors.ResultsIn contrast to Wnt3a-conditioned media, media supplemented with recombinant Wnt3a alone did not support long-term survival of human or mouse colon organoids. Mechanistically, this observation can be attributed to the fact that recombinant Wnt3a did not support stem cell survival or proliferation as demonstrated by decreased LGR5 and Ki67 expression. When monitoring expression of markers for epithelial cell types, the highest level of organoid differentiation was observed after combined removal of Wnt3a, Noggin, and R-spondin from Wnta3a-conditioned media cultures.ConclusionOur study defined Wnt3a-containing conditioned media as optimal for growth and survival of human and mouse organoids. Furthermore, we established that the combined removal of Wnt3a, Noggin, and R-spondin results in optimal differentiation. This study provides a step forward in optimizing conditions for intestinal organoid growth to improve standardization and reproducibility of this model platform.

Download Full-text

Motility in multicellular Chlamydomonas reinhardtii (Chlamydomonadales, Chlorophyceae)

10.1101/201194 ◽

2017 ◽

Author(s):

Margrethe Boyd ◽

Fran Rosenzweig ◽

Matthew Herron

Keyword(s):

Chlamydomonas Reinhardtii ◽

Radiant Energy ◽

Culture Conditions ◽

Wild Type ◽

Unicellular Alga ◽

Trade Off ◽

Directional Movement ◽

Volvocine Algae ◽

History Of

AbstractThe advent of multicellularity was a watershed event in the history of life, yet the transition from unicellularity to multicellularity is not well understood. Multicellularity opens up opportunities for innovations in intercellular communication, cooperation, and specialization, which can provide selective advantages under certain ecological conditions. The unicellular alga Chlamydomonas reinhardtii has never had a multicellular ancestor yet it is closely related to the volvocine algae, a clade containing taxa that range from simple unicells to large, specialized multicellular colonies. Simple multicellular structures have been observed to evolve in C. reinhardtii in response to predation or to settling rate-based selection. Structures formed in response to predation consist of individual cells grouped within a shared transparent extracellular matrix. Evolved isolates form such structures obligately under culture conditions in which their wild type ancestors do not, indicating that newly-evolved multicellularity is heritable. C. reinhardtii is capable of photosynthesis, and possesses an eyespot and two flagella with which it moves towards or away from light in order to optimize input of radiant energy. Motility contributes to C. reinhardtii fitness because it allows cells or colonies to achieve this optimum. Utilizing phototaxis to assay motility, we determined that newly evolved multicellular strains do not exhibit significant directional movement, even though the flagellae of their constituent unicells are present and active. In C. reinhardtii the first steps towards multicellularity in response to predation appear to result in a trade-off between motility and differential survivorship, a trade-off that must overcome by further genetic change to ensure the long-term success of the new multicellular organism.

Download Full-text

Morphological Changes of Rhizobia in Peat Cultures

Applied and Environmental Microbiology ◽

10.1128/aem.68.3.1064-1070.2002 ◽

2002 ◽

Vol 68 (3) ◽

pp. 1064-1070 ◽

Cited By ~ 13

Author(s):

Lu Feng ◽

Rodney J. Roughley ◽

Les Copeland

Keyword(s):

Cell Wall ◽

Manganese Superoxide Dismutase ◽

Cultured Cells ◽

Morphological Changes ◽

Wall Thickening ◽

Term Survival ◽

Manganese Superoxide ◽

Enhanced Expression ◽

Iron Manganese

ABSTRACT Morphological changes that take place in peat cultures of several species of rhizobia were examined. These changes seemed to be associated with enhanced survival of cells in peat and after inoculation onto plastic beads, which were used as a model system for seeds. Cell wall changes, in which the periplasmic space appeared to be occluded with electron-dense material, were observed in Rhizobium sp. strain SU343 and Bradyrhizobium lupini WU425 cells after 7 and 14 days in peat, respectively. Nutrient limitation and low O2 concentration in peat are suggested to be factors involved in the induction of the morphological changes. Polyhydroxybutyrate reserves, which were present in broth-cultured cells of both species of rhizobia, were mobilized after transfer into peat but did not appear to influence survival after inoculation onto beads. Enhanced expression of an iron-manganese superoxide dismutase was also observed after the cells were transferred into peat. We conclude that cell wall thickening in rhizobia after transfer from broth cultures into peat is an adaptive response for long-term survival under nutrient-limited conditions in peat. Cells with thickened walls may also be more resistant to other types of stress, such as that encountered on a seed surface.

Download Full-text