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HISTO3003 > Inductive interactions (wk 5) > Flashcards

Inductive interactions (wk 5) Flashcards

1
Q

Which type of cell specification is typical of insects?

A

Synctial

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2
Q

Which type of cell specification is typical of invertebrates?

A

Autonomous

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3
Q

Conditional specification is typical of what type of organism?

A

Vertebrates (and some invertebrates)

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4
Q

Which two molecules form a gradient within a single cell during syntical formation?

A

bicoid and nanos

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5
Q

In mosaic development, can cells change their fate if a blastomere is lost?

A

No

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6
Q

What type of development does conditional specification give rise to?

A

Regulative development

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7
Q

What factor is important during conditional specification?

A

Position

Based on interactions with its environment

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8
Q

Mosaic development relies on ______ where as regulative development relies on ______

A 
Mosaic= importance of segregation of determinants
Regulative= importance of inductive interactions
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9
Q

T/F:
Taking a cell that would normally rise to ICM in mammals and move it to the outside it will form ICM on the outside of the blastocyst

A

False

if you get to it early enough you can move the cell to the outside and it will now become trophoblast cells

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10
Q

What is the ectoplacental cone?

A

Pre-cursor to the placenta

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11
Q

Which cells invade the uterine wall and what do they eventually form?

A

Synctiotrophoblast cells invade

They form the ectoplacental cone which is the pre-cursor for the placenta

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12
Q

Distinguish between the polar and mural trophoblast

A 
Polar= closest to the ICM
Mural= furthest away from the ICM
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13
Q

T/F:

Mural trophoblast attaches to the uterine wall

A

False

Polar trophoblast does

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14
Q

What happened when they removed the mural trophoblast cells and inserted ICM cells within it?

A

ICM had an effect on the mural trophoblast cells

Ectoplacental cone started forming which doesn’t happen in normal situations

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15
Q

__ cell sends an ____ signal to the ____ cell

A

Inducer cell sends an inductive signal to the responsive cell

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16
Q

T/F:

Morphogens are insoluble molecules

A

False

Soluble

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17
Q

What are the three types of ways cells can interact with each other?

A

Diffusion
Matrix
Direct

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18
Q

Distinguish between instructive and permissive inductive interactions

A

Instructive

  • The underlying tissue provides a specific signal to the overlying tissue
  • Type of underlying tissue is important to achieve the desired differentiated tissue

Permissive
- The tissue underneath provides a general signal, doesn’t have to be specific to get the desired differentiated tissue

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19
Q

What are the two important factors needed for any inductive interaction?

A
  1. The nature and presentation of the inductive signal

2. The competence of the responding tissue

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20
Q

Which process causes the ectoderm to differentiate into two different tissues? What are the two tissues?

A

Neuralation
Epidermal ectoderm
Neuroectoderm

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21
Q

Where does the neural groove arise?

A

At the primitive streak

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22
Q

List some things that the epidermal ectoderm and neuroectoderm give rise to

A

epidermal ectoderm gives rise to skin (epidermis), lens, inner ear, hair, nails, mammary glands

neuroectoderm gives rise to neural tube (CNS; brain, retina, nervous system) neural crest cells -cranial and sensory ganglia, head mesenchyme

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23
Q

T/F:

Epidermal ectoderm pinches off to form the optic vesicle

A

False

Neuroectoderm

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24
Q

How does the lens placode form?

A 
Optic vesicle (vagination of the neural tube) makes contact with the overlying epidermal ectoderm
Epidermal ectoderm responds and thickens
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25
Q

T/F:

Lens placode is thickened neuroectoderm

A

False

Thickened epidermal ectoderm

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26
Q

How does the optic vesicle become the optic cup?

A

Lens placode starts to invaginate and form the lens pit which causes the optic vesicle to collapse and eventually form the optic cup

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27
Q

What role does Shh play in eye development?

A

Ensures that two optic vesicles form
Knockout= only one forms
Cyclocephaly-cyclopia
(nasal prominence is also missing)

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28
Q

T/F:

Lens vesicle forms when the lens pit pinches off from the epidermal ectoderm

A

True

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29
Q

T/F:

Optic cup forms the cornea

A

False
Optic cup forms the retina
Overlying epidermal ectoderm (overlying the lens vesicle) forms the cornea

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30
Q

What are the primary fibres and where do they form?

A

They are the cells facing the developing retina (optic cup)

They are elongating

31
Q

What does the optic stalk form?

A

The optic nerve

32
Q

If you move the optic vesicle to another epidermal ectoderm what happens?

A

Lens placode can’t form because the ectoderm is not competent

33
Q

What is the double assurance hypothesis

A

Notice a lentoid structure forming when the optic vesicle was not present

Concluded that the lens would normally arise by contact with the optic vesicle, but failing this, could arise separately if necessary

34
Q

What three things is the head lens ectoderm exposed t during embryogenesis?

A

Presumptive pharyngeal endoderm
Presumptive heart mesoderm
Optic Vesicle

35
Q

What are the primary induces that will establish competence and lens bias of ectoderm?

A

Endoderm (future pharynx)

Mesoderm(future heart)

36
Q

What is the secondary inducer that initiates lens morphogenesis

A

Optic vesicle (future retina)

37
Q

T/F:

Primary fibres have Pax 6 switched off

A

True

38
Q

List one thing that differentiates lens epithelium and lens primary fibres

A

Primary fibres do not contain Pax 6 but lens epithelium does

39
Q

T/F:

Pax 6 is not present in the optic cup

A

False

40
Q

What happens when you knock out pax 6?

A

Nasal plate/nose is deformed

No eye forms

41
Q

T/F:

Surface ectoderm requires expression of Pax6 in order to respond to the inductive optic vesicle

A

True

42
Q

What produces solutes that populates the aqueous to provide nutrients and growth factors for the ocular environment?

A

Cillary body and Iris

43
Q

Where is the proliferative hot spot for lens epithelial cells?

A

Germinal zone

44
Q

Where do the lens epithelial cells start to become cuboidal and elongate into secondary fibre cells to allow the lens to grow?

A

Transition zone

45
Q

What makes the lens transparent?

A

Crystallins

46
Q

T/F:

Alpha crystallin is present in epithelial and fibre cells

A

True

47
Q

T/F:

Beta and gamma crystallin is present in epithelial cells

A

False

Only present in fibre cells

48
Q

How are the deeper layers of lens cells organised?

A

Ball and socket joints

  • lose their smooth borders
  • stick together using the ball and socket
  • Important structural feature
49
Q

How are the fibres of the centre of the lens organised?

A

More disorganised than the secondary fibre cells

50
Q

What shape are the lens cells and why?

A

Hexagonal shape
Really efficient way of packing
Prevents the scattering of light

51
Q

Why are ball and socket interactions necessary?

A

The cillary body has zonula fibres attached to the lens which moves the lens –> this movement can cause the fibre cells to slide to it is important there is structural strength

52
Q

T/F:

When the cillary body muscle relaxes the lens will flatten

A

True

53
Q

What comprises 95% of the tissue volume of the lens?

A

Fibre cells

54
Q

What happens at the lens suture?

A

Elongating fibre cells arc around the lens equator, fibre tips will converge at the lens poles where they interlock to form the suture

55
Q

What structural feature can be seen on the superficial lens fibres that confers structural stability?

A

Interlocking edge protusions between cells

56
Q

What is degraded in the fibre cells near the centre of the lens to provide optical clarity?

A

Organelles

Here it is the organelle free zone

57
Q

What is the shape of the suture? Why?

A

Y shape

Allows more cells to meet at a common point

58
Q

What are the epithelial cells bathed in?

A

Aqueous

59
Q

T/F:

The aqueous contains something that causes the epithelial cells to differentiate into fibre cells

A

False

It is the vitreous that is causing the differentiation

60
Q

T/F:

FGF (fibroblast growth factor) induces epithelial cells to elongate and become fibre cells

A

True

61
Q

T/F:

Lens epithelial cells gain pax6 and connexin43 when FGF is added

A

False

They lose it

62
Q

List some things that occur when lens epithelial cells are exposed to FGF

A

Differentiate into fibre cells
Downregulate Pas6 and connexin43
Elongate
Induct beta and gamma crystalins, connexin 50 (communication), filensin, phakinin
Induces denucleation and ball and socket joints

63
Q

T/F:

All ocular tissues including the lens express various types of FGF

A

True

64
Q

T/F:

FGF is expressed only in the Vitreous

A

False

Also expressed in the Aqueous but the epithelial cells don’t have the right receptor here and won’t respond to it

65
Q

T/F:

If lens epithelial cells express a small dose of FGF they will differentiate

A

False
Small dose= only proliferate
Need a large dose to differentiate

66
Q

T/F:
Vitreous contains higher concentrations of FGF than the aqueous therefore cells exposed to the vitreous will differentiate and those exposed to the aqueous wont

A

True

67
Q

T/F:

More FGF is located anteriorly compared to posteriorly

A

False
Other way round
Gradient from anterior to posterior

68
Q

What is the role of TGFbeta?

A

Induces epithelial mesenchymal transition in cataract and posterior capsule opacification (secondary cataract)

69
Q

What is a cataract?

A

Any opacification of the lens

70
Q

What type of response is seen in a cataract?

A

Fibrotic response
Cells flatten and overlap
Contain particular cytoskeleton proteins not normally produced
TGFbeta induces the fibrosis

71
Q

When exposed to TGFbeta, what type of cytoskeletal protein is expressed?

A

alpha smooth muscle actin (alpha SMA)

72
Q

T/F:
Exposure to TGFbeta causes the production of ECM components such as laminin, HSPG, collagen I and III, fibronectin, tenascin

A

True

73
Q

Where can you see EMT in adults?

A

Wound healing
Cancer metastasis
Fibrotic pathologies

74
Q

What is PCO?

A

Posterior Capsule Opacificaiton is a long term complication with cataract surgery

Lens cells grow on the posterior capsule, modify the proteins as well, can produce wrinkling

HISTO3003 (6 decks)

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