Ultrastructure of Human Gastrointestinal System. Interactions Among Mast Cells, Eosinophils, Nerves and Muscle in Human Disease.
William J. Snape, Stephen M. Collins in Effects of Immune Cells and Inflammation on Smooth Muscle and Enteric Nerves, 2020
MC are mononuclear cells filled with secretory granules (Figures 20 & 21). Other cytoplasmic organelles include mitochondria, intermediate filaments, lipid bodies, Golgi structures, small vesicles, and ribosomes. Surface processes are narrow folds. The granules are filled with dense materials, assuming several patterns. These include homogeneously dense material, scrolls, crystals, particles, and mixtures of these patterns. These granule patterns in aggregate are unique to human MC. MC that are present in situ in normal gastrointestinal tissues, as well as those examined after isolation from human colons, are well-preserved cells which generally contain scroll-filled and particle-filled granules. MC that are present in, or isolated from, the gut contain more particle-filled granules than do MC from other locations. MC from the lung, for example, contain more scroll granules; those from skin contain more crystal granules. Ultrastructural visualization of MC does not depend on dye-binding, as does light microscopic visualization of MC. Poor fixation of electron microscopic samples produces broken membranes and cytoplasmic and nuclear damage. All of these changes are visible — that is, certain fixatives do not render MC invisible to imaging with electrons.
Biology of microbes
Philip A. Geis in Cosmetic Microbiology, 2006
Fungi are typical contaminants in a few products that contain limited water and have low pH values; many of these products are lotions and creams. Fungi are eukaryotic: they contain membrane-surrounded organelles, particularly membrane-bound nuclei within which is the DNA comprising the chromosomes. Other membrane-enclosed organelles include the mitochondria (which once were bacteria according to the endosymbiont hypothesis), the Golgi apparatus, endoplasmic reticula, lysosomes, and nucleoli (where ribosomes and ribosomal RNA are made). The term organelle is used to emphasize the parallel between the organs of animals and the structures within cells, each of which performs a very specific function. The extensive membrane systems in eukaryotes are needed because of their large volume and their need for regulation and transport as a result of that large volume.
The Cell and Cell Division
Anthony R. Mundy, John M. Fitzpatrick, David E. Neal, Nicholas J. R. George in The Scientific Basis of Urology, 2010
In the adult human, cells are continuously being lost by the process of planned, programmed cell death (apoptosis). Some cells do not divide at all, although they can be destroyed (neurons and skeletal muscle fibers; however, recent work on stem cells suggest that these continue to exist in brain and muscle into adult life): some divide slowly, and others have to divide rapidly (such as cells in the bone marrow and lining of the gut). During cell division, DNA is replicated and reproduction of intracellular organelles takes place. Replication of DNA takes place during a specific part of mitosis known as the S phase. G2 is the period of rest before the prophase part of the M phase starts. The G1 phase occupies the period between the completion of the previous mitosis and the S phase; some mature cells, however, enter a specialized period of rest, G0, which can last for months or years. The proportion of dividing cells can be measured by a number of different tests. Administration of radiolabelled thymidine or bromodeoxyuridine can allow labeling of cells in the S phase to be demonstrated by the use of photographic plates or monoclonal antibodies, respectively. Other antibodies can be used to measure the Ki67 antigen (Ki67 or MIB1) or proliferating cell nuclear antigen, which are expressed during particular parts of the cell cycle; these are useful in measuring cell proliferation within tumors. The amount of DNA within a population of cells can be estimated by the use of fluorescent stains such as ethidium bromide measured in a fluorescence-activated cell sorter.
Tissue-specific organelle DNA degradation mediated by DPD1 exonuclease
Published in Plant Signaling & Behavior, 2011
Lay Yin Tang , Wataru Sakamoto
Organelle DNA in plastids and mitochondria is present in multiple copies and undergoes degradation developmentally. For example, organelle DNA that is detectable cytologically using DNA-fluorescent dye disappears during pollen development. Nevertheless, nucleases involved in this degradation process remain unknown. Our recent study identified the organelle nuclease, DPD1, which has Mg2+-dependent exonuclease activity in vitro. The discovery of DPD1 emerged from Arabidopsis mutant screening and concomitant isolation of dpd1 mutants that retain organelle DNA in mature pollen. DPD1 is conserved only in angiosperms: not in other photosynthetic organisms. Despite these findings, the physiological significance of organelle DNA degradation during pollen development remains unclear because dpd1 exhibits no apparent defects in pollen viability or in the maternal inheritance of organelle DNA. We discuss a possible role of organelle DNA degradation mediated by DPD1, based on a DPD1 expression profile studied using in silico analyses.
CDK Control of Membrane-Bound Organelle Homeostasis
Published in Cell Cycle, 2006
Heidi M. Blank, James M. Totten, Michael Polymenis
In eukaryotes, the copy number and size of any given organelle compartment remain constant in dividing cells, underlying a tight coordination between cell division and organelle homeostasis. However, in most cases the mechanisms for this coordination remain mysterious. Here we outline a few cases where the cell cycle machinery directly impacts on organelle homeostasis, with emphasis on the control of vacuolar (lysosomal) copy number and size in budding yeast. We also discuss aspects of organelle biology that can profoundly affect certain cell cycle parameters, such as cell size.
Analysis of mitochondrial and chloroplast genomes in two volvocine algae:
Published in European Journal of Phycology, 2019
Yuxin Hu, Weiyue Xing, Huiyin Song, Guoxiang Liu, Zhengyu Hu
ABSTRACT The colonial volvocine algae span the full range of organizational complexity, from four-celled species to multicellular species, and this group of algae is often used for the study of evolution. In recent years, many organelle genomes have been sequenced using the application of next generation sequencing technology; however, only a few organelle genomes have been reported in colonial volvocine algae. In this study, we determined the organelle genomes of Eudorina elegans and Eudorina cylindrica and analysed the organelle genome size, structure and gene content between these volvocine species. This provided useful information to help us understand the composition of colonial volvocine organelle genomes. Based on the chloroplast genome protein-coding genes, we conducted a phylogenomics analysis of the volvocine algae. The result revealed an unexpected phylogenetic relationship, namely, E. elegans is more closely related to Pleodorina starrii than to E. cylindrica. The substitution rate of volvocine algae was then calculated based on organelle genome protein-coding genes; our analysis suggested the possibility that the two Eudorina species may be under similar evolutionary pressure. Lastly, the synteny analysis of the mitochondrial genome showed that gene arrangements and contents are highly conserved in the family Volvocaceae, and the synteny analysis of the chloroplast genome indicated that the genus Eudorina may have experienced genomic changes.
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