Bio 127 Section III axis Formation



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Bio 127 Section III

  • Axis Formation

  • General background

    • A single mRNA added may introduce a second organizer power causing drastic change.

    • Blastula has no axis.

    • Doral-Ventral Axis

    • Anterior-Posterior Axis

    • Left-RT Axis

  • Relationships between chick and frog

    • Chicken

      • Hypoblast- dorsal vegetal cells. Organizer.

      • Koller sickleHensen’s nodeprimitive streak

    • Frog

      • Koller sicklepre-dorsal lip; mesoderm

      • Wnt and FGF signals from hypoblast

      • Organizer(endodermal cells) secretes noggin and BmP7 and Dickoeff

    • Yolk Positioning

      • Eggs are rotated rt angle to gravity

    • Specification of the chicken anterior-posterior axis

      • Complex signals from notochord

      • Positional specification by gravity

      • Hox genes

    • Rostral-Caudal

      • Hox genes

    • Left-RT

  • Stem Cells

  • General background

    • Each system has stem cell niche

    • Most cancers arise from regeneration prone cells

    • Stem cell-cell that produces one stem cell and one differentiated cell (asymmetric mitosis)

    • Fast divisions occur in bone marrow, gut , and skin

    • Slow divisions occur only in stress or repair: heart, and prostate

    • 1 trillion cells live in us, 1 out 10 are human

  • Terminology

    • Totipotent

    • Pluripotent

    • Multipotent

    • Unipotent

  • Types of Stem cells

    • Inner cell massembryonic stem cell

    • Hematopeitic

    • Mesenchymal

    • Epidermal

    • Gut

    • Mammary

    • Melanocyte

    • Muscle

  • Location(niche)

    • Bone marrow

      • Hematopoietic stem cellsmultipotentmyeloid progenitor cell

      • Control on differentiation

        • Bone cell matrix

        • Stromal paracrine factors

        • Pericyte paracrine factors

        • Systemic hormones

        • Neuronal signals

      • Enzymes

    • Mouse tooth

      • Balance of positive and negative signals

        • FGF3 Vs BMP3

        • Activin Vs Follistalin

        • Combination of two systems for differentiation and division

    • Drosophila testes

      • Hubs cell hold centrioles

        • Somaic cells

        • Control rate

      • Organizer pathway

        • Hub cellsunpairedjak-Stat stem cell division

        • Stem cell stays bound and diff cell moves away

    • Niche Breakdown

      • Too much cell differentiation

      • Craps out

  • Ectoderm

  • General background

    • GastrulaNervous system

    • First organ system made

    • 2 major steps

      • Formation of neural tube

      • Differentiations of neurons

    • NC forms PNS

    • Pregnant women take folic acid

    • Stimulation of neural folding begins at the front as hensen node is migrating back

    • Primary and secondary neuralation begins at regression of hensen node

    • Further anterior, more complex

  • Neuralation

    • Primary

      • Formation and Folding

      • Elevation

      • Convergence

      • Closure

        • 3 pts of closure

      • Doesn’t form posterior neural tube

      • NotochordMHPepiboly from ectodermMHP flattens causes wedge shape bendsecond hinge dorsolateralfolds over NC migrates outFolate binding proteine-cadherin to n-cadherinneural link

    • Secondary

      • Far posterior

      • Epithelialdelaminate to form mesenchymemedullary chordrecoilless to solid mass of cellapoptosis in middle to form hollow tubereestablish connectionsform other layer

  • Three simultaneous levels of development in tube

    • Gross anatomy

    • Tissue anatomy

    • Cell biology

  • Early human Brain Development

    • Primary vesicles: Forebrain, midbrain, hindbrain

    • Secondary vesicles: Telencephalon, Diencephalon, mesencephalon, metacephalon, myelencephalon.

  • Dorsal-Ventral axis specified by ectoderm and notochord signals

  • Increase Buldging and increase neurons

  • Differentiation of neurons in the Brain

    • Three types

      • Neurons

      • Glia

        • Astrocytes

        • Oligodendrocytes

      • Ependymal

    • 1 output(axon and neurotransmitter)

    • 1-100,000 inputs

    • Axon has microspikes for migratory traction

  • Neuron birthday

    • Nucleus location determine cell life cycle

  • Three layers in Spinal Cord

  • Six layers in Cerebellum

  • 12 layers in Cerebral Cortex

  • Development of Sensory System




  • Neural Crest

  • General background

    • CNS regulation

    • Bugging out the neural tube

    • Advancement to vertebrates

    • Most cells in NC are multipotent pregenitors and determined fate

    • Multipotent progenitor not a stem cell

    • Specificity in position and determine fate by migratory path

  • Cranial NC

    • Many potentials (18) ex. Thyroid, thymus gland, tendon

    • Endocrine power vs CNS

  • Cardiac NC

    • Smooth muscles located in large outflow arteries

      • After heart is made by mesodermNC cause apoptotic distruction to smooth muscles in major outflow arteriesreplace smooth muscles

    • NC tissue not prone to cancer or blockage

  • Trunk NC

    • Two Directions

  • Vagosacral NC

    • Migrate to form medulla

    • Sympathetic interneurons

    • Parasympathetic interneurons

  • Pre-patterning and Plasticity

  • Neural and Axons Specification

  • General background

    • 100 billion neurons in the adult

      • 300 billion born

      • Race of neuronal and sk muscle connections

  • Determined by anterior-posterior position and hox genes leaves neuron competent to certain interneuron or sk muscle connections

  • Co-expression


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