Nucleus and Mitosis VIBS 443 and VIBS 602 Undergraduate Graduate Histology Lecture Series Larry Johnson, Professor Veterinary Integrative Biosciences Texas A&M University College Station, TX 77843
Objectives Characterize the interphase nucleus including the cell cycle, nucleolus, chromatin, nuclear envelope, and nucleocytoplasmic interactions. Characterize mitosis including structures with definitions, mechanisms of chromosome movements, and cytokinesis.
Remember the proposed evolutionary involvement of the cell membrane in organelle formation. Eukaryotic cell Eukaryotic cell
Nucleus (interphase nucleus) Microtubules Intermediate filaments Stabilize nuclear envelope
Nucleus - archive of the cell Archive of the cell - nucleus encodes for all proteins and secretory products. All somatic cells have the same codes regardless of their final function in the body (e.g., nerve, epithelium, CT, muscle).
Heterochromatin - condensed chromatin Euchromatin dispersed for active transcription Nucleus Cells in an individual are the same in their genome, but they differ in its expression.
Nucleus Source of major informational macromolecules that direct protein synthesis. trna, mrna, and, rrna
Chromatin Nucleus Nucleoprotein - stain basic dye Nuclei
Cell cycle Generation time varies with cell type 4-6 days in intestine absorptive cells Year in nerve cells
Cell cycle G1/S/G2/M GAP 2 M Mitosis GAP 1 S DNA synthesis GAP 1 GAP 2
Cell cycle Morphology varies with the cell cycle. Shown by differential interference contrast microscopy.
Dead stained cells Bright field Live unstained cells Phase contrast Nomarski differential interference contrast Dark field
Phase contrast light microscopy Cell cycle The cell cycle - cells round up for mitosis
http://www.youtube.com/watch?v=rglj rvox_qo http://www.youtube.com/watch?v=dd 3IQknCEdc&featur e=related http://www.youtube.com/watch?v=q6uckwiifmg&feature= related
Nucleolus Cell fractionation to study nucleoli morphology - ribosome production Fibrous 50 A 45S 18S + protein 40S (small subunit) Granular 120 to 150 A 45S 28S + protein 60S (large subunit)
Nucleolus Metabolic activity of cell reflected in size of nucleolus Pituitary cell If axon is cut, size of nucleolus increases by 50% Oocyte Sertoli cell Leydig cell Nerve cell
Nucleolus To study the pathway of ribosome formation: Pulse chase experiment 3 H uridine for RNA Temporal appearance of radioactivity revealed that 3 H uridine first was seen over the nucleus, then nucleolus, and finally over the cytoplasm.
Nucleolus Ribonucleoproteins - Have an affinity for basic dyes and are the most conspicuous of stained nuclear organelles.
Nucleolus Disperses in cell division
Nucleolus Contains genes for ribosomal RNA.
Nucleolus Is essential for protein synthesis destined for cytoplasm. Note contribution of: Cytoplasm Nucleus Nucleolus to ribosomal production
Nucleolus Summary Pulse chase experiment 3 H uridine for RNA, Temporal appearance of radioactivity revealed that 3 H uridine first was seen over the 1) Nucleus, 2) Nucleolus, and finally over the 3) Cytoplasm 3 H uridine for RNA
Chromatin DNA double helix w/ protein 20 A thick Mitosis 500-1000 A thick
Chromatin 100s of miles of DNA in single cell packaged for mitosis. Beads on a string
Chromatin Heterochromatin sperm cell nucleus, inactive and dark Euchromatin nerve cell nucleus, active and light
Chromatin Histones and other proteins from cytoplasmic ribosomes
Polyribosomes
Nuclear envelope Cell membrane is involved in organelle formation. Outer membrane - continuous with RER Inner membrane space - cisterna of RER
Nuclear envelope Nuclear pores nuclear cytoplasmic exchange Pore size 40 to 100 A Number = 2000/nucleus
Nuclear envelope Nuclear pores Gold study 80-100 A Nucleoplasmins are molecular chaperones that transfer the DNA to the histone-dna complexes by binding to the histones.
Nuclear envelope Nuclear pores Ribosomal large subunit 120 to 150 A squeezes through 40 TO 100 A Pore size = 40 to 100 A
Nuclear envelope Nuclear pores
Nuclear envelope Nuclear pores DNA not associated w/ pores RNA always associated w/ pores
Nuclear envelope Fibrous lamina or (nuclear lamina) Intermediate filaments
Annulate lamellae = nuclear pores like structures in RER
Why chromosomes, kinetochores, and centrioles? Chromosomes super coil prevents errors during mitosis Kinetochores most important part for division or segregation of chromosomes
Why chromosomes, kinetochores, and centrioles? Many plants have no centrioles If a centriole is removed, the cells still divide Real function unknown, except they are needed to be present to be pasted to the daughter cell for what ever their function is
Microscopy that allows observation of live cells.
Why do cells divide? Allow organism to increase in mass Replace damaged cells Reduce size of cell - improved diffusion
Why do cells divide? Avoid aging build up of waste products. If a portion of a cell is removed, it prevents cell division.
Mitosis Defined - cell division in which duplicated chromosomes divide into daughter cells that have identical chromatin content Mitotic figures in gut epithelium
Mitosis Cell division in gut epithelium
MITOSIS Definitions Karyokinesis - nuclear division Cytokinesis - division of cytoplasm Completion in 30 min to 2.5 hrs Cells in mitosis in intestinal epithelium
Chromosomes - rod-like organelles, visible during cell division Number of chromosomes Diploid - 2n - full complement Haploid - 1n - half complement Polyploid - more than full complement (Down s syndrome)
Chromosomes rod-like organelles, that are visible during cell division Gene - hypothetical units of inheritance Linearly arranged along length of DNA Gene locus Deletion Translocation
Three main events in mitosis 1. Orientation (after chromosomal condensation and nuclear envelope breakdown) 2. Alignment 3. Segregation
MITOSIS
ORIENTATION ALIGNMENT SEGREGATION
Events in mitosis Cytokinesis
Events in mitosis Cytokinesis
Events in mitosis Cytokinesis
Events in mitosis Cytokinesis
Events in mitosis Centrosome separation
Mechanisms of chromosome movement Microtubule assembly - disassembly model Sliding microtubules model
http://www.youtube.com/watch?v=vln7k1-9qb0&feature=related http://www.highlighthealth.com/did-you-know/mitosis-and-meiosis/
Chromosome movement Kinetochore, polar, and astral microtubules
Chromosome movement
Chromosome movement
Chromosome movement Three contributions 3 Kinetochore 1 Polar 2 Astral 1) polar, 2) astral, and 3) kinetochore microtubules
Chromosome movement
http://www.youtube.com/watch?v=2wwikd ybn_s&feature=related http://www.youtube.com/watch?v=6dmlde9akbk&feature=related
Mitosis Developing ovarian follicle has many cells in mitosis.
Next time Peripheral blood
Many illustrations in these VIBS Histology YouTube videos were modified from the following books and sources: Many thanks to original sources! Bruce Alberts, et al. 1983. Molecular Biology of the Cell. Garland Publishing, Inc., New York, NY. Bruce Alberts, et al. 1994. Molecular Biology of the Cell. Garland Publishing, Inc., New York, NY. William J. Banks, 1981. Applied Veterinary Histology. Williams and Wilkins, Los Angeles, CA. Hans Elias, et al. 1978. Histology and Human Microanatomy. John Wiley and Sons, New York, NY. Don W. Fawcett. 1986. Bloom and Fawcett. A textbook of histology. W. B. Saunders Company, Philadelphia, PA. Don W. Fawcett. 1994. Bloom and Fawcett. A textbook of histology. Chapman and Hall, New York, NY. Arthur W. Ham and David H. Cormack. 1979. Histology. J. S. Lippincott Company, Philadelphia, PA. Luis C. Junqueira, et al. 1983. Basic Histology. Lange Medical Publications, Los Altos, CA. L. Carlos Junqueira, et al. 1995. Basic Histology. Appleton and Lange, Norwalk, CT. L.L. Langley, et al. 1974. Dynamic Anatomy and Physiology. McGraw-Hill Book Company, New York, NY. W.W. Tuttle and Byron A. Schottelius. 1969. Textbook of Physiology. The C. V. Mosby Company, St. Louis, MO. Leon Weiss. 1977. Histology Cell and Tissue Biology. Elsevier Biomedical, New York, NY. Leon Weiss and Roy O. Greep. 1977. Histology. McGraw-Hill Book Company, New York, NY. Nature (http://www.nature.com), Vol. 414:88,2001. A.L. Mescher 2013 Junqueira s Basis Histology text and atlas, 13 th ed. McGraw Internet images and videos on biological presentations