20. reproductive tox

What day does implantation occur

Day 7 in rates, day 6 in mice

What happens after implantation

Embryogenesis - all tissues get identified

What occurs after embryogenesis

Fetal development until parturition

Recommended lactation window

6 months

how many segments is reproductive cycle divided into

3

Segment 1 of reproductive cycle

From gamete to zygote : gametogenesis, fertilization and up to implantation

Segment 2 of reproductive cycle

From implantation to birth - all tissues develop

Segment 3 of reproductive cycle

from birth to adult

T or F all gametes in females are formed before birth

T

Primordial follicle

follicle with 1 layer of cells around egg

Primary follicle

when cells are expanding

Antrum

Space in middle of growing follicle

Corpus luteum

what is left of follicle after ovulation

How to move from arrested primordial follicle to primary follicle

LH and FSH stimulation

Meiosis only occurs in

2 cell types: egg and sperm

T or F many follicles but only 1 ovulates

true

Why is if difficult to demonstrate effect of toxicant on follicle

Most follicles die anyway, only 1 moves on to ovulation each month
hard to tell if its toxicant or natural death

What happens to corpus luteum if no fertilization

Shrinks

Which reproductive toxicology is more studied male or female

male (difficult to demonstrate effect of toxicant on follicle)

LH surge function

triggers ovulation + progesterone

What causes LH surge in female

Caused by rise in estradiol coming from growing follicle

FSH function in female

stimulates follicle growth

What produces Progesterone

corpus luteum

Progesterone function

Stimulates cell growth and secretion from the uterus

If progesterone levels go down

menstruation

What does mitogenic mean

stimulates cell division

Which hormone is mitogenic

Estrogen - stimulates cell division

What does estrogen do to uterus

Acts on uterus to cause cell division

What is a good model to study reproductive toxicology

Rat - has similar cycle to human menstrual cycle

What releases LH and FSH

anterior pituitary

What causes pituitary to release LH and FSH

Hypothalamic release of GnRH

What releases prolactin

Anterior pituitary

Most extensively studied chemical that affects female reproductive system

Chemotherapeutic agents

T or F women treated for cancer almost always can remain fertile after

F - almost always infertile

Nitrogen mustard, cyclophosphamide and 5-florouracil have what in common as mechanism for toxicity

All affect cell division by
1. Blocking meiosis
2. Blocking cell division of granulosa cells that surround the egg
3. Preventing growth of follicle

First index toxicologists use

body weight

T or F production rate of sperm is about the same throughout different ages

T

Function of leydig cells

Make steroids

Function of sertoli cells

provide structural and metabolic support to the germ cells

T or F toxicants can work directly on germ cell division in meitosis, meiosis and maturation

T

What can antibiotics do to affect male reproductive system

block fertilization

what can some metals do to male reproductive system

spermatogenesis by affecting ability for chromosomes to condense properly

Seminiferous tubules have what cells

both leydig and sertoli

All carbons in a steroid molecule come from

from acetyl CoA

What is the mother of all steroids

cholesterol

T or F - affecting leydig cells will also affect spermatogenesis

T

90% volume of testis is

germ cells (sperm)

Why would testes shrink

spermatogenesis has arrested

What happens when testes shrink

Can see many more leydig cells - impression that its leydig cell hyperplasia which is not the case
must understand physiology to study tox

Where must toxicant target to have immediate effects

Epididymus or last phase of the maturation process

How long does spermatogenesis take

2.5 months for men
rate 30-50 days
delayed response to toxicant

What happens when one cell divides in mitotic division during spermatogenesis

cells dont separate - bridges connecting them all

Function of bridge

To transport gene products across cells
some Y bearing sperm need the input from gene products of X bearing sperm

Where do X rays hit in male reproductive system

spermatogonia

Where does cyclophosphamide hit

anti cancer drug that hits cells when they are spermatids

Chlorambucil

germ cell toxicity

Acrylamide hit wehn

hits spem when they are completed

Blood testes barrier

Sertoli cells form projections and make tight junctions between each other
cells beyond this point are protected from targets of toxicants

How can toxicants get through blood testes barrier

Sertoli cells are moving, if you affect them before they form the junctions the toxicants will be carried with them

Which cells have the most DNA repair machinery in the body

germ cells

Why do germ cells have the most DNA repair machinery

When they go through meiosis there is a cross over between chromosomes, lots of breaks happen at that point

Effect of Vit A in male reproduction

Critical for entry into meiosis
Deficiency causes arrest in spermatogenesis

Effect of Zinc in male reproduction

Responsible for chromatin compaction, however too much of it can cause damage

Vitamin E in male reproduction

Source of antioxidants
deficiency can be toxic

List of gonadotoxic drugs

Busulfan
Chlorambuxcil
Cyclophosphamide
Nitrogen mustard
corticosteroids

What type of drugs are gonadotoxic drugs

Chemotherapeutic

What doe gonadotoxic drugs do to male reproductive system (all in common)

affect meiosis

WHat happens to sperm in epididymus

Aquire ability to swim and recognize egg

Epidiymis

single long tube where sperm are transported matured and stored in the cauda

How is sperm pushed out when ejaculation occurs

Tail of cauda contracts and pushes sperm out of vas deferens to urethra

T or F sperm are not affected in epididymus

F - can be affected as it passes through

Most common end points used to asses male reproductive toxicants

Semen analysis

What is looked at in sperm analysis

Volume
Sperm motility
Morphology of sperm

Who has better quality sperm humans or rats

Rats

Computer aided semen analysis

Take video of sperm swimming - can see actual path taken, distance travelled and movement

WHat is important for sperm fertilizing activity

Calcium channels

Effects of heart drugs on fertility

Many BP drugs are calcium channel blockers
calcium channels important for sperm fertilizing ability
side effects for many hypertensive drugs \= infertility

Difference in DNA between sperm and somatic cells

6x more compacted in sperm

Protamines

Allow reorganization of the chromatin in a tight compaction by displacing histones

What happens to protamines as they pass through epididymus

Get crossed linked

Chromatin biomarkers to assess sperm chromatin quality

Ability of sperm to decondense
Breaks and cross links and integrity of chromatin
Chromatin template function
Chromatin structure
Chromatin epigenome

Comet assay main function

tox test used to assess DNA damage in somatic cell

Comet assay method

apply the cells in electric field
if there is a break in DNA it will migrate further
more it migrates the smaller the DNA the greater the fragmentation

Tunnel assays look at

DNA breaks

Chromatin structure assay

Look at amount of protamine, the ability to make disulphide bridge, and epigentic marks

What kind of test to study drugs that require bioactivation to become toxic in male reproduction

In vivo
in vitro sperm lose their metabolizing functions

T or F can reduce the sperm in rats by 95% before seeing effects on fertility

T

Why is weight a sensitive marker of spermatogenesis

because 90% of weight is sperm

Histology is better for

telling you info on target cells

Con of histology

subjective

Comparison of histology vs. testes weight vs fertility vs gene expression as marker of spermatogenesis

Weight \= less sensitive, but is rapid, simple
Histology \= more sensitive, subjective
Fertility \= Very insensitive but if change is seen, can confirm it has an effect
Gene expression \= overly sensitive, can be repaired before damage is done

Correlation between testes and sperm count

Decr of testes weight by 10% - always see that sperm count it decreased

T or F changes in genes indicates that a toxicant will have an effect on progeny

F - not necessarily
often able to repair damage

T or F sex is determined by mother

F sperm carries either X or Y

Sex ratio in ontario

decline in proportion of males
cause undetermined but area was near a large number of industries with contaminated water and soil

Trend of sperm count in US and europe

50% decline - many confounding factors, more study needed

Maternal smoking on progeny

can have effect on sperm count of progeny

Trend of testicular cancer

rising all over the world

Age range of incidence of testicular cancer

18-35 - unfortunate as this is age when want to have children

Testicular dysgenesis syndrome cause

Genetic and/or environmental factors