L13 Growth (Imported from Quizlet)

Cell growth is differentially regulated to maintain what?

The correct proportions and to drive morphogenesis

What is meant by hypertrophy?

Getting larger

Rates of division must be carefully regulated to maintain what?

Cell numbers in a given tissue

After early development, division is ______ -> typically one division every 24 hours in proliferating mammalian cells

Slower

Other cells do not divide once they are _____ and last for many years

Born

During DNA replication, each chromosome (maternal and paternal) is _________ to give rise to ________ __________

Duplicated, sister chromatids

Sister chromatids must be distributed (segregated) into ...?

Daughter cells

Cell cycle has how many stages?

Four

G phase is the ______ phase

Gap

G1 can be very ______ or even _________

Long, permanent

Most cells are in which phase?

G1

S phase is ...?

Replication

M phase is ...?

Dividing cells and chromosomes

Cell cycle has different checkpoints (yellow boxes) to ensure what?

That a cell does not enter mitosis unless needed

These checkpoints have to do with making sure everything is in order before _________ and _____________

Mitosis, cytokinesis

Which is the important checkpoint in development?

Start

Checkpoint genes are often mutated in tumours to do what?

Enable cell proliferation (e.g. retinoblastoma, Rb)

What does retinoblastoma inhibit?

Division

Overall growth is important in setting ...?

The adult size

What regulate the secretion of GH?

Somatostatin, GHRH

Body size is centrally controlled by ...?

Hormones

Three ________ feedback loops acting on growth hormone proliferation, these interactions must be __________

Negative, balanced

What is IGF and what does it do?

Insulin-like growth factor, acts more locally to drive cell proliferation

What is GH and what does it do?

Growth hormone, made in the pituitary, secreted ind he blood and drives growth, acting on liver and bone, drives proliferation, activates IGF

How is IGF regulated once it is activated by GH?

Negative feedback loop turns down secretion of GH

What is GHRH?

Growth horomone-relasing hormone

Organs have ways of _________ their own _____

Measuring, size

What is meant by ablation?

Destruction

A strain of mice is generated that carries an introduced gene for diphtheria toxin under the control of what?

A tetracycline repressible promoter

Regulation of organ size by _____ and _______ pathways

TOR, Hippo

TOR pathway promotes ...?

Cell growth

Hippo pathway promotes ...?

Cell death (apoptosis)

Hippo inhibits _______ ____________ -> turn down the rate of cell division

Cell proliferation

Mutations in hippo cause ...?

Organ hypertrophy

Apoptosis is deliberate _______ of an _______ cell

Suicide, unwanted

What does apoptosis involve?

Careful coordination of the shut down of the cell -> followed by engulfment of the remnants by other cells

Apoptosis is caused ___________ by stress such as _________ or excessive _____ ________

Intrinsically, starvation, DNA damage

When is apoptosis used?

During development to cull unneeded cells

What is apoptosis used for in adult tissue?

Homeostasis (liver and mammary gland) and health (e.g. to get rid of infected, viral or genetically compromised tumour cells) and in the immune system ensure self reactive cells are removed

What can cause necrosis?

Injury, infection, cancer, infarction and inflammation

What is necrosis?

Disorderly, dying off of cell without any signal to or from the neighbouring cells

What happens to the cells during necrosis?

They split open and empty their contents into surrounding tissue

Myostatin is secreted/produced by ...?

Muscle

What does myostatin provide?

Negative feedback on muscle growth

Mutations that affect myostatin activity cause what?

Increased muscle mass

Myostatin reduces ________ _________ and ________ ___________

Myoblast proliferation, muscle differentiation

MyoD important in differentiation into _______ ______ -> myostatin blocks this

Muscle fibres

Myostatin activates ____ -> inhibits _____ ___________

Rb, cell proliferation

Removal of a kidney leads to what?

Increase in size of the remaining kidney

Why does this happen when you remove a kidney?

In response to a temporary rise in the concentration of creatinine in circulation (signals the need to increase kidney function)

The increase in kidney size is the result of ...?

Cell enlargement (hypertrophy)

The liver produces and regulates what?

Bile levels

Artificially increasing bile acid in circulation causes the liver to ______ in response, the _______ is the result of ___ _________. This leads to bile levels being ________ by liver absorption

Grow, increase, cell proliferation, reduced

Skeletal growth drives what?

Body growth

Most of the skeleton is formed as a _________ _________ in the embryo

Cartilage template

Most bones form initially as _________, over time bone cells secrete _____ to form _________ ________

Cartilage, bones, skeletal structure

Over time what is formed on the cartilage template?

Bone

What is a chondrocyte?

Cartilage cell

What is a osteoblast?

Bone cell

Where does cartilage remain?

In the joint areas

In long bones, chondrocyte proliferation drives what?

Post natal growth

Growth plates are formed by ...?

Chondrocytes

Chondrocytes are ___________ and then _______ in cell size (hypertrophy) give rise to ________ cells, invasion by __________ converting it to _____

Proliferating, increase, larger, osteoblast, bone

Once osteoblast converts larger cells into bone, _________ occurs and then ______ _______ is laid down in its place

Apoptosis, bone matrix

Growth driver at the _________ (between bone and cartilage caps) called the _______ ________

Interphase, growth plate

The growth plates close at the end of _________, all the chondrocytes ____ ____, all filled in with ____ ________

Puberty, die off, bone matrix

High levels of androgens in the ring finger ________ ______

Promote growth

High levels of oestrogen in the ring finger _________ ______

Repress growth