journal article 3

What does “multiparous” mean?

Cows in their 2nd or later lactation

At what week of lactation were cows ovariectomized?

Week 8

What were the two treatment groups?

Ovx (ovariectomized) and Sham (control surgery)

What was measured to assess estrogen sensitivity in mammary cells?

ERα protein levels and % ERα-positive epithelial cells

What reference protein was used in Western blots?

β-actin

What is DAPI used for in the study?

To stain DNA in immunohistochemistry

What technique was used to measure lactoferrin and BSA?

Radial immunodiffusion

What does gelatin zymography measure?

Proteolytic (gelatinase) enzyme activity

Why did the researchers measure BSA in milk?

To evaluate tight junction leakage

How did ovariectomy affect plasma estradiol (E2)?

It significantly lowered E2 but did not reduce it to zero

Why is E2 not zero in Ovx cows?

Extra-gonadal tissues still produce small amounts of estrogen

What additional evidence supported reduced estrogen production in Ovx cows?

Lower uterine weights at slaughter

What happened to lobule number in Ovx cows?

They had fewer lobules per µm²

What happened to lobule size in Ovx cows?

Their lobules were larger

Why do larger lobules matter?

They contain more active secretory epithelium

How did alveolar lumen size differ between groups?

Ovx cows had enlarged alveolar lumens

What does enlarged alveolar lumen indicate?

Higher milk storage and ongoing secretion activity

Which cows produced more milk: Ovx or Sham?

Ovx cows

Why did Ovx cows produce more milk despite fewer lobules?

They had more secretory activity per lobule due to larger, more active structures

How does estrogen normally influence lactation length?

Estrogen promotes mammary remodeling and eventual involution

What effect does removing ovarian hormones have on lactation?

It delays involution and increases lactation persistence

Which group had higher gelatinase activity at week 52?

Sham cows

What does higher gelatinase activity indicate?

Greater tissue breakdown and active involution

Why do gelatinases increase during involution?

They degrade extracellular matrix to remodel mammary tissue

Which cows had increased BSA in milk at week 52?

Sham cows.

What does increased BSA in milk reveal?

Leakier tight junctions

What does leaky tight junctions indicate about the gland state?

It is progressing toward involution

Why did Ovx cows maintain lower BSA levels?

They had better epithelial barrier integrity and slower involution

What happens to lactoferrin production as involution begins?

It increases

Why does lactoferrin increase during involution?

It protects mammary tissue as milk production declines

Which cows expressed more ERα protein at week 52?

Sham cows (~24% higher)

Why does higher ERα matter?

It means greater mammary responsiveness to estrogen

What percentage of epithelial cells in Sham cows were ERα-positive?

6.7%

What percentage were ERα-positive in Ovx cows?

1.3%

What was the major physiological conclusion of the study?

Ovariectomy delays mammary involution and extends lactation persistence

How does this support lecture concepts on endocrine control?

It provides direct evidence that ovarian hormones regulate milk production and involution

What cellular markers showed that Sham cows were further along in involution?

Higher gelatinase activity, higher BSA leakage, smaller alveolar structures

What structural markers showed Ovx cows were still actively lactating?

Larger alveolar lumens, preserved epithelial integrity, lower proteolysis

Why is this study important for understanding dairy cow lactation?

It links hormonal status (particularly estrogen loss) to changes in tissue structure, milk composition, and lactation persistence