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Nucleus and Mitosis Histology Lecture Series

Nucleus and Mitosis Histology Lecture Series

Undergraduate – Graduate Nucleus and Lecture Series

VIBS 443 and VIBS 602 Larry Johnson, Professor Veterinary Integrative Biosciences Texas A&M University College Station, TX 77843 Objectives Characterize the nucleus including the cycle, , , , and nucleocytoplasmic interactions.

Characterize mitosis including structures with definitions, mechanisms of movements, and cytokinesis. Remember the proposed evolutionary involvement of the cell in formation.

Eukaryotic cell

Eukaryotic cell Nucleus ( interphase nucleus) Intermediate filaments Stabilize nuclear envelope Nucleus - archive of the cell Archive of the cell - nucleus encodes for all and secretory products. All somatic cells have the same codes regardless of their final function in the body (e.g., nerve, , CT, muscle).

Heterochromatin - Nucleus Cells in an individual are the same in their condensed , but they differ in its expression. chromatin – dispersed for active Nucleus Source of major informational that direct synthesis.

tRNA,

mRNA,

and, rRNA Nucleus Chromatin – - stain basic

Nuclei

Cell cycle

Generation time varies with cell type – 4-6 days in intestine absorptive cells – Year in nerve cells

GAP 2 G1/S/G2/M

M – Mitosis

GAP 1

S – DNA synthesis GAP 1 GAP 2 Cell cycle Shown by differential Morphology varies with interference contrast the cell cycle. 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 - 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 Nerve cell Nucleolus

To study the pathway of ribosome formation: Pulse chase experiment – 3H uridine for RNA

Temporal appearance of radioactivity revealed that 3H uridine first was seen over the nucleus, then nucleolus, and finally over the . Nucleolus Ribonucleoproteins - Have an affinity for basic and are the most conspicuous of stained nuclear . Nucleolus

Disperses in

Nucleolus Contains 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 – 3H uridine for RNA,

Temporal appearance of radioactivity revealed that 3H uridine first was seen over the 1) Nucleus, 2) Nucleolus, and finally over the 3) Cytoplasm 3H 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 – cell nucleus, inactive and dark

Euchromatin – nerve cell nucleus, active and light

Chromatin and other proteins – from cytoplasmic Polyribosomes

Nuclear envelope is involved in organelle formation. Outer membrane - continuous with RER Inner membrane space - 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 -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 () Intermediate filaments Annulate lamellae = nuclear pores like structures in RER Why , kinetochores, and ?

Chromosomes – super coil prevents errors during mitosis

Kinetochores – most important part for division or segregation of chromosomes Why chromosomes, kinetochores, and centrioles?

– Many have no centrioles – If a 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 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 - 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

SEGREGATION ALIGNMENT

Events in mitosis

Cytokinesis Events in mitosis Cytokinesis

Events in mitosis Cytokinesis

Events in mitosis Cytokinesis

Events in mitosis separation

Mechanisms of

chromosome movement 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 1 Polar Kinetochore 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 Developing ovarian follicle has many cells in mitosis.

Mitosis Next time Peripheral

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 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 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 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, 13th ed. McGraw • Internet images and videos on biological presentations

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