ANS 124: Branches & Alveoli

What type of cell signaling is happening during ductal elongation due to the coordinated actions of GH, E and IGF-1?

Paracrine Signaling

(the cells responding to these signals were not the ones making it)

During luteal phase, the cells are responding to what 2 hormones? Via what receptors?

Estrogen via ER

Progesterone via PR

During Luteal Phase, the actions of Estrogen and Progesterone leads to what in the epithelial cells?

Ductal Side Branch Formation (due to mitosis)

In an experiment looking at whether the epithelial cells with PR and ER also divide, what 2 things would you label? How would you label it?

Label dividing cells with green by detecting BrDU they tagged themselves with during mitosis.

Label the PR in cells with red using an antibody to find the PR.

What are 2 methods to finding where the PR are in cells (that was discussed in lecture)?

Immunohistochemistry

Use LacZ gene to visualize it.

Describe where the red cells (with PR) and the green cells (mitotic) were found in the mammary duct after being labeled.

The red cells and green cells were next to each other with pretty much no overlap.

Since there is no overlap in the red and green cells, what does that mean?

That the red cells with PR/ER are not creating an autocrine signal to induce themselves to do mitosis.

Red cells are NOT dividing!

Since the red cells (with PR) and the green cells (mitotic) were found next to each other, what are 2 potential ways that the cells with PR/ER are inducing mitosis in the green cells?

Could be...

a paracrine signal from the red cell directly to the green cell to induce mitosis.

the red cell sending a paracrine signal to another cell in the stroma, which then sends a paracrine signal to induce mitosis in the green cell.

When does Tertiary Side Branching happen? (2)

Might happen during the Luteal Phase.

Also continues during the first part of Pregnancy.

Tertiary Side Branching during the luteal phase is due to the effects of what 2 hormones?

Estrogen & Progesterone

Does the effect of Progesterone require a paracrine molecule to convey its effects?

Yes!

What is the name of the molecule that is required for progesterone's action on the mammary gland?

Hepatocyte Growth Factor (HGF)

Hepatocyte Growth Factor (HGF) induces process what in the mammary gland?

induces mammary epithelial cells to branch

(by inducing cells to do mitosis and to form tubes)

HGF to Progesterone is just like _____ to _____.

IGF-1 to GH

Since Hepatocyte Growth Factor (HGF) is a 'growth factor', what type of molecule is it?

a protein (polypeptide)

Is Hepatocyte Growth Factor (HGF) a mitogen? Why or why not?

It is not because it doesn't ONLY tell the cells to divide.

Since Hepatocyte Growth Factor (HGF) is not a mitogen, what is it then? Why?

HGF is a morphogen because it tells cells to divide in a certain way (to form slender long ducts that are the branches of the mammary gland).

What is the set-up of an experiment that was investigating the effects of HGF on the mammary gland?

Epithelial cells from the mammary gland were put in a jello-like substance (collagen) in a culture dish. The cells were given HGF and then the effects were observed.

What happened to the epithelial cells treated with HGF in the experiment that was investigating the effects of HGF on the mammary gland?

They started to have branching morphogenesis where the epithelial cells formed long, slender ducts.

What cells produce HGF?

Fibroblasts

What cells do HGF act on in a paracrine manner?

HGF acts on epithelial cells.

HGF acts on epithelial cells via what? (general)

via a receptor for HGF

What is inducing the Fibroblasts to synthesize HGF?

The red labeled cells with ER and PR.

What is another morphogen in the mammary gland that is similar to HGF?

Transforming Growth Factor beta (TGF)

What was the set-up of the experiment that was investigating the effects of TGF on the mammary gland?

The same as the HGF experiment with the epithelial cells in the petri dish, except TGF was given.

How is TGF different compared to HGF?

TGF beta's effects are concentration dependent.

At LOW concentrations, what does TGF Beta induce in the mammary gland?

Acts as a morphogen, stimulates tube/duct formation.

At HIGH concentrations, what does TGF Beta induce in the mammary gland?

Inhibitory effects.

Since at high concentrations, TGF Beta is inhibitory to ductal growth, what does it do?

It makes sure that the ducts don't grow too close to each other since they need to have a spacing of at least 0.25mm apart.

With each estrous cycle, what 2 hormones are produced from the ovaries?

Estrogen & Progesterone

With each estrous cycle, Estrogen increases Progesterone Receptors where?

in the epithelial cells

With each estrous cycle, Progesterone acts to increase production of what 2 molecules?

HGF

Maybe low-level TGF Beta?

With each estrous cycle, does it lead to primary, secondary or tertiary branching?

Tertiary Branching

With Tertiary Branching, the ducts are now receptive to what process?

ducts now receptive to adding alveoli if pregnancy occurs (and will continue to add alveoli to new side branches that developed during early pregnancy as well)

What is the main process that is happening during pregnancy in the mammary gland?

Alveolar Development

During pregnancy, what 2 important hormones does the anterior pituitary produce?

Prolactin

Growth Hormone

Are PRL and GH coded for by the same gene? Explain.

No, they have 2 distinct genes, but they probably evolved from 1 common gene in the beginning.

PRL has a relative hormone called ___________ ___________.

Placental Lactogen (PL)

Where is Placental Lactogen (PL) produced?

Placenta

What process does Placental Lactogen (PL) contribute to in the mammary gland during pregnancy?

alveolar development

The Anterior Pituitary is controlled by what structure in the brain?

Hypothalamus

What is produced in the Hypothalamus that inhibits the production of PRL from the Anterior Pituitary?

Dopamine

As daylength/photoperiod gets longer, what happens to PRL levels in the blood circulation?

PRL increases in circulation

Why does PRL increase in the circulation when the daylength/photoperiod gets longer?

in order to time pregnancy and parturition for when there is abundant nutrition for lactation

In Humans, what happens to the levels of hPL, E2, P, and PRL during gestation?

They all increase. (increases the most right before the end of pregnancy)

In Rodents, what happens to the levels of PL, E2, P, and PRL during gestation?

PL, PRL, and E2 all increase right before parturition. P is increased throughout gestation and then drops right around the time of parturition.

What are antibodies?

molecules that bind to antigens

If looking at a blood sample from a pregnant individual, how can you find how much hormone is in the sample using antibodies? (general)

Blood sample has antigens (PL, PRL, GH, E/P). You can use a specific antibody on the blood sample to find how much antigen is in the sample.

What is the name of a procedure that can be used to find the amount of antigen/hormone is in the blood sample?

ELISA (Enzyme Linked Immunosorbent Assay)

Describe how an ELISA works on a blood sample.

Antibodies for what you're trying to find in the sample is added to the sample. An enzyme is added, which can attach to the antibodies in the sample. When antibodies attach to their target, we get 1 unit enzyme activity. Add substrate for the enzyme that will change color when antibodies attach to their target. Use the proportion of reaction through spectroscopy/spectrophotometer to measure concentration of hormone/antigen.

In order to find a numerical number for the concentration of the hormone/antigen in the blood sample, what must be done beforehand?

A standard curve must be plotted with samples of known concentrations of the hormone/antigen with X = known concentration and Y = reaction outcome.

When we measure the unknown sample, we can measure reaction outcome and use the standard curve to calculate the concentration of hormone/antigen.

What 2 processes does Prolactin induce in the mammary gland?

Alveolar Development

Lactogenesis (initiate lactation)

Prolactin also induces the production of what molecule in the mammary gland?

induces IGF-II in the mammary gland

(similar to GH inducing IGF-I production!)

IGF-1 is produced by what cells in the mammary gland?

cells of the stroma

IGF-2 is produced by what cells in the mammary gland?

epithelial cells

IGF-2 acts on what cells? It acts in what type of fashion?

IGF-2 acts on itself (epithelial cells) in an autocrine fashion.

When IGF-2 acts on itself in an autocrine fashion, what process is it inducing?

alveolar development