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Lectures Flashcards

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1
Q

What is sex determination?

A

The development of characteristics allowing an individual to be identified as male or female
Reproductive system, phenotype, behaviour, hormones, metabolism

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2
Q

From the bipotential gonad, describe the mechanism of sex differentiation in the male

A

Y chromosome - Testis determining factor encoded by SRY gene - SOX-9 activation - stimulates testis development - steroidogenic factor 1 - Sertoli cells produce AMH to regress female duct - Leydig cells produce testosterone to develop male organs from Wolffian duct

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3
Q

From the bipotential gonad, describe the mechanism of sex differentiation in the female

A

X chromosome - DAX1/Wnt4a activation - stimulates follicular and theca cells in ovary for follicle growth - follicles product oestrogen - oestrogen causes development of female organs from Mullerian duct

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4
Q

In high temperatures what happens to aromatase? What may happen to reptile sexes?

A

Is increased, so increased androgen-oestrogen conversion which increases female offspring or can cause male-female conversion (vice versa in cold)

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5
Q

What is the sex allocation hypothesis?

A

Female mammals are able to adjust offspring sex ratio in response to their maternal condition. I.e. in deer, dominant males father all offspring, subordinate males do not mate. All females get pregnant but only higher rank ones produce sons that can mate. So to maximise reproductive output, dominant females should produce males and lesser females should produce females as all females are impregnated.

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6
Q

What is adaptive control of gender bias?

A

Changing offspring sex bias in response to changing environment - food, population, disease. I.e. if low population density, skews bias towards males as these disperse to fertilise other colonies and maximise genetic potential

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7
Q

Explain the difference between differential fertilisation and differential embyro survival?

A

Differential fertilisation - more male or female sperm selected for fertilisation
Differential embryo survival - more male or female embryos aborted

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8
Q

Name 4 places in the female reproductive tract sperm progression is controlled?

A

Cervix - mucus removes DNA damaged sperm as have poor motility
Uterus - neutrophils remove membrane damaged sperm
Utero-tubal junction - prevents 90% of sperm in uterus entering oviduct to reduce polyspermy
Oviduct - storage in reservoirs and controlled release to give access to oocyte

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9
Q

Explain the control of sperm progression at the UTJ

A

Molecular recognition system in place. Some sperm unable to pass UTJ despite normal motility and morphology due to lack of surface proteins i.e. ADAM1. Lack of these mean unable to bind to ZP.

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10
Q

What is the glycoprotein that causes the negative charge of sperm? What does the negative charge correlate with?

A

CD52 which is involved in sperm binding. Negative charge correlated with DNA integrity and state of maturation so CD52 is a marker of genetic integrity

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11
Q

What is the set of genes controlling acquired immunity? Is this involved in mate choice?

A

Major histocompatibility complex (MHC). Females choose partners with MHC different to their own - more sperm at oocyte when parental MHC differs

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12
Q

How do X and Y sperm differ?

A

By around 3/4% nuclear content, X sperm is longer, different proteins expressed influencing motility and metabolism, individual sperm microRNAs

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13
Q

What is reproductive intervention? Name 5 types.

A

Methods directed at helping individuals to overcome infertility/assist animal production
IVF, AI, ICSI, ET, cloning

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14
Q

What is genetic management?

A

Aiming to avoid inbreeding

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15
Q

What is the extinction vortex?

A

Small population leeds to inbreeding, disease, inbreeding depression, smaller population and extrinction

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16
Q

Explain the difference between in vivo and in vitro embryo transfer

A

In vivo - superovulated cows mate naturally, embryos are flushed from tract and transferred, can be split into multiple
In vitro - ovaries obtained from dead, oocytes extracted and matured then inseminated and transferred when embryo forms

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17
Q

What is cloning?

A

Taking a cell line from a valuable animal and injecting the somatic cell nucleus into an enucleated oocyte from another, which then develops into an embryo in a foster mother

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18
Q

What are the stages or preimplantation development?

A 
2 cell stage
4 cell stage
8 cell stage
Morula
Blastocyst
Hatched blastocyst
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19
Q

When does compaction occur?

A

16-32 cell morula stage

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20
Q

What are the components of the blastocyst?

A

Trophectoderm (outer layer)
Inner cell mass
Blastocoele cavity

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21
Q

What is compaction?

A

The stage preceding blastocyst where cell to cell adhesion increases, outer cells become polarised and form the trophectoderm and inner cells form the inner cell mass, and there is formation of a cavity

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22
Q

What molecule drives compaction?

A

E-cadherin, a transmembrane cell:cell adhesion molecule

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23
Q

Name 4 other molecules important for compaction

A

Calcium
Protein kinase C (relocated E-cadherin)
Alpha catenin
JAM-1 (junctional adhesion molecule)

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24
Q

What are the 2 cell polarisation models at compaction?

A

Inside/outside hypothesis where cell position directs cell fate
Cell polarity hypothesis where cell fate drives the positioning

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25
What factors prevents loss of fluid out of the embryo resulting in expansion to blastocyst?
Polarised distribution of Na/K ATPase in the membrane Established an ion gradient of high Na in blastocoele, facilitating water movement in through aquaporins Tight junctions preventing loss of fluid
26
Name 4 key molecules important in the blastocyst, expressed in the ICM or trophectoderm
Oct4 - ICM Nanog - ICM Gata6 - ICM Cdx2 - trophectoderm
27
Explain how energy metabolism differs between oocyte to blastocyst
At compaction embryo switches from dependence on TCA cycle in early cleavage, to glycolysis metabolism as blastocyst. So the ATP energy gained from oxidation decreases and ATP produced increases
28
State the changes in lactate, glucose and pyruvate uptake/production from oocyte to blastocyst
Lactate production increases Glucose uptake increases Pyruvate stays around the same - surpasssed by glucose
29
How does glucose uptake relate to embryo viability?
Glucose uptake is higher in a viable embryo. | Very high glycolysis is associated with non viable embryos
30
What is the optimum O2 level for embryo culture? | Name 3 reasons why
5% 20% (atmospheric) leads to more alteration in gene expression, higher amino acid turnover in early cleavage stages and low in blastocyst, lower cell numbers
31
What functions do amino acids serve? Name 5
Essential for embryo development. | Protein synthesis, metabolism, chelation, pH regulation, energy
32
How does amino acid turnover relate to embryo viability?
Embryos with high amino acid turnover at early cleavage stage have low viability compared to those which have steady increase in turnover as they get to blastocyst stage
33
Name 3 outcomes of abnormal embryo development
Fragmentation Loss of blastomeres Arrest
34
In early cleavage stage, faster embryos... (glucose, lactate, glycolysis)
High glucose consumption | Low lactate consumption and glycolytic rate
35
In blastocyst stage, faster embryos... (glucose, lactate, glycolysis)
Increased glucose uptake, lactate production and glycolytic rate
36
Name 3 substrates and 3 products that may be used as biomarkers for embryo viability
Glucose, pyruvate, amino acids uptake | Lactate, ammonium, amino acids production
37
How does oxygen consumption of the embryo change?
Increases sharply at blastocyst stage
38
Define infertility. How many couples are affected?
If a woman has not become pregnant after 1 year of regular sexual intercourse without contraception. Affects 1/6 of couples
39
What day does fertilisation occur to form zygote?
Day 0
40
What day does first cleavage to 2 cell stage occur?
Day 1/2
41
What day does 4 cell stage occur?
Day 2/3
42
What day does compaction occur? (morula)
Day 3/4
43
What day does blastocyst enter uterus?
Day 5
44
What day does hatching occur?
Day 6/7
45
What are 3 essential factors for embryo implantation?
Receptive endometrium Healthy blastocyst Communication between mother and baby
46
Name 3 features of non receptive endometrium
Long apical microvilli, high surface negative charge, thick mucin layer
47
Name 3 features of a receptive endometrium
Shorter microvilli, loss of surface negative charge, thinning of mucin coat, formation of pinopodes
48
What is decidualisation?
Postovulatory process of endometrial remodelling in preparation of pregnancy. Includes secretory transformation of uterine glands, influx of NK cells, vascular remodelling. Progesterone driven
49
What are the 3 stages of embryo implantation?
Apposition, adhesion, invasion
50
What is an inhibitory molecule for attachment?
Mucin1
51
What are promoting molecules for attachment?
Leukaemia inhibitory factor, adhesion molecules (E-cadherin, integrins)
52
What are molecules involved in invasion?
MMPs, TIMPs, PGs, COX-2, IL-11, VEGF
53
What type of implantation occurs in humans?
Invasive interstitial implantation
54
How long is the embryogenic phase?
14 days from conceptus to embryo
55
How long is the embryonic phase?
6 weeks from embryo to foetus
56
How long is the foetal phase?
220 days until birth
57
What does the corpus luteum do?
Synthesises progesterone to maintain pregnancy until the placenta takes over at around 12 weeks
58
What did the dutch famine birth cohort study find?
In utero exposure to famine affected the offspring - coronary heart disease in 1st trimester, obstructive airways disease in 2nd and high blood pressure and mental health disease in 3rd
59
What is the Barker early origins/foetal origins hypothesis?
Low weight in infancy increases death from ischaemic heart disease
60
What does a low birth weight predispose to?
CV disease, type 2 diabetes, osteoporosis, depression
61
What does a high birth weight predispose to?
Cancer
62
What is cellular differentiation?
Process by which genotype gives rise to phenotype
63
What is epigenetics?
Inheritable changes in organisms caused by modification of gene expression rather than changes in the genetic code itself
64
Name 2 types of epigenetic modification
Methylation, histone acetylation
65
What is developmental plasticity?
Selection of the right phenotype to fit the anticipated future environment
66
What does the maternal-embryonic communication regulate? Name 3
Blastocyst morphogenesis Implantation coordination Maternal immunotolerance Developmental plasticity
67
What facilitates sperm transport?
Sperm motility and female tract movement
68
What is capacitation?
The final maturational stage of sperm that takes place in the female genital tract before sperm gain ability to fertilise oocyte, increasing viability and motility
69
Where is sperm stored in the human and for how long?
Sperm can be stored in reservoirs in the fallopian tubes for up to 5 days
70
What is the benefit of sperm storage?
Increased motility, viability, delayed time to capacitation so longer lifespan of sperm
71
What are 2 changes that occur in the oviduct in response to sperm presence?
Altered protein secretion Changes in transcription I.e. adrenomedullin secretion increases at sperm contact with oviduct, increasing ciliary beat frequency
72
What modulates the periconception environment?
Short range signals - local responses to gametes | Long range signals - hormones, environment, nutrition
73
What is the purpose of ZP3?
Mediates primary sperm binding and acrosome reaction
74
What is the purpose of ZP2?
Mediates secondary sperm binding
75
What is the purpose of ZP1?
Forms a crosslink between 2 and 3 as a protein network
76
What is the cortical reaction?
Occurs when a sperm binds to the oocyte membrane. Increased calcium results in mobilisation of cortical granules to the membrane, and release into perivitelline space, where they act on ZP to prevent further binding
77
What is the acrosome reaction?
Occurs when a sperm binds to the ZP. Acrosome swells, membrane binds to the overlying plasma membrane, large increase in Ca2+ and contents of acrosomal vesicle are exocytosed out. These enzymes digest the ZP to allow sperm to reach oocyte
78
What are 3 patterns of fertility behaviour?
Starting, stopping, spacing
79
What is fecundity?
Physiological capability of a woman to produce a live birth
80
What is fertility?
How many live births actually achieved by a woman
81
What is prospective cohort analysis?
How many children a woman has over her lifetime, following her as it happens i.e. by population register
82
What is retrospective cohort analysis?
How many children a woman has HAD over her lifetime, collected i.e. by medical history or survey after childbearing age
83
What is period analysis?
Number of births in a particular time period, collected i.e. by birth register
84
What is parity progression ratio?
Cohort measure | Proportion of women with at least 'n' children who go on to have at least one more child 'n+1' (expressed P01, P12)
85
What is crude birth rate?
Period measure Ratio of live births in a time period i.e. one year to the average population in that period, expressed as births per 1000 population (births/population x1000)
86
What is general fertility rate?
Period measure | Births per 1000 women aged 15-49
87
What is age specific fertility rate?
Period measure | Births per 1000 women aged a certain age (x)
88
What is total fertility rate?
Period measure expressed as cohort measure - synthetic cohort measure Number of children who would be born to a woman if she lived to the end of her childbearing years and had children in accordance with current age specific fertility rates
89
What are 5 lowest fertility countries?
Taiwan, Macao, Hong Kong, Singapore, South Korea, Moldova, Bosnia and Herzegovina, Portugal, Spain, Hungary
90
What are 5 highest fertility countries?
Niger, Somali, Mali, Chad, Angola, Congo, Burundi, Uganda, Timor-Leste, Gambia
91
What is immunology?
Study of the defence mechanisms of an organism
92
Name the types of pathogen
Bacteria, virus, fungi, parasites
93
What is immunity?
Protection from infectious disease
94
What are the 3 branches of the immune system?
Physical and chemical barriers Innate immune system Adaptive immune system
95
What are the 5 signs of inflammation?
Heat, redness, swelling, pain, loss of function
96
What are 4 aspects of the innate immune system?
Physical barriers - skin Immediate action - anti microbial peptides Non specific - pattern recognition receptors Leukocytes - neutrophils, NK cells, dendritic cells, macrophages
97
What are pattern recognition receptors?
Germ line encoded receptors which can recognise pathogen associated molecular patterns (PAMPs) synthesised by microorganisms
98
What are toll like receptors?
PRRs which recognise PAMPs and initiate downstream signalling events, leading to release of cytokines/chemokines/anti microbial peptides which cause recruitment of neutrophils and macrophages and maturation of dendritic cells
99
What are 2 aspects of the adaptive immune system?
Cellular effectors - cytotoxic/helper T lymphocytes | Humoral effectors - B lymphocytes secrete antibodies
100
Name 3 differences between the innate and adaptive immune system
Innate - early recognition, low specificity, no memory | Adaptive - late recognition, specific, long memory
101
What are potential sources for infection of the female tract?
Menstruation, fertilisation, implantation, pregnancy, parturition
102
How does the innate immune system facilitate events of the female tract?
Helps passage of sperm Facilitates implantation Enables pregnancy to continue
103
How does oestradiol affect immunity?
Increases susceptibility to infection, allows sperm into the tract
104
How does progesterone affect immunity?
Increases immune surveillance
105
What are the 3 immunological phases of pregnancy?
1 - implantation and placentation resemble an open wound and elicit strong inflammatory response 2 - growth in the second trimester 3 - renewed inflammation promoting contractions and birth
106
How does immune system respond to implantation in the decidua?
DCs, NK cells, macrophages infiltrate decidua and accumulate around embryo, without these there is negative effect on development
107
What is immune tolerance?
Reducing impact of a pathogen without actually fighting it - i.e. pregnancy
108
Describe the grading system of early cleavage embryos
3 numbers representing the number of cells, degree of ideal cells, and degree of fragmentation (higher numbers better) 8, 4, 4 = best quality 8 cell embryo 5, 1, 1 = worst quality 5 cell embryo
109
Describe the grading system of blastocyst embryos
Grade 1-4 for degree of expansion and 5-6 for hatching (higher numbers better) If 3 or higher, further graded A-D for ICM and trophectoderm (A highest)
110
What is implantation?
Series of stages including blastocyst hatching, adhesion, endometrial invasion, embryo differentiation and growth to produce a state of clinical pregnancy
111
What is implantation rate?
Number of embryos implanted over number transferred in a given time period
112
What is repeated implantation failure?
Failure to reach clinical pregnancy (gestational sac/foetal heartbeat on USS) after the transfer of at least 4, good quality fresh or frozen embryos in a women <40 over at least 3 transfer cycles
113
When is the implantation window?
Day 6-10 after fertilisation
114
What cell types does the trophoblast differentiate into?
Cytotrophoblast | Syncytiotrophoblast
115
What is the objective of ART?
To bring sperm and oocyte closer together to increase chances of fertilisation and pregnancy
116
Give 3 reasons for ART
Infertility, absence of a partner, genetic engineering
117
State each step of the IVF-ET procedure
Superovulation and egg collection - semen collection - insemination - fertilisation check - embryo culture - embryo transfer (/cryopreservation) - luteal support - pregnancy test
118
State the procedure of oocyte collection
Monitor follicular development by TVUSS, and when at least 2 follicles are 17mm diameter give hCG to induce maturation and aspirate with a catheter
119
Name methods of sperm selection
Percoll swim up DNA probe stains - SYBR14 Flow cytometry Fluorescence activated cell sorting
120
When is ICSI used?
If sperm are unable to fertilise - abnormal morphology, motility, damaged acrosome, immature
121
What is PGD?
Pre implantation genetic diagnosis. Used to screen embryos for genetic disorders
122
How is PGD performed?
At 8 cell stage (2/3 days), zona drilling performed to remove 1/2 blastomeres to screen for disease
123
What is CRISPR-Cas9 used for?
Enables gene editing for identification, removal and replacement of faulty genes
124
Explain how CRISPR-Cas9 works
Clustered regularly interspaced short palindromic repeats - CRISPR - RNA sequence generated to reflect sequence of target gene CRISPR RNA coupled with the restriction enzyme Cas9 CRISPR-Cas9 complex injected into cell Target sequence snipped out of DNA by Cas9 to disable gene Synthetic DNA can be spliced at the restriction zone to introduce a desired trait
125
How much semen and sperm do men ejaculate?
Men ejaculate 5ml of semen with 250 million sperm
126
What is migration efficiency?
The distance (mm) travelled by sperm in 7 minutes
127
What 2 things does high fertility need?
Competent sperm | Sufficient duration
128
What are ROS?
Reactive oxygen species, important in capacitation/acrosome reaction/binding but oxidative stress can cause damage to sperm DNA
129
What is cryopreservation?
When a substance is preserved by cooling to very low temperatures to stop any processes that would cause functional or material damage
130
What are the 3 steps in cryopreservation?
Cooling Freezing Thawing
131
What are the 4 requirements of sperm cryopreservation?
Retain an intact plasma membrane Cell function should not be impaired Organelles should be intact and functional DNA should be intact
132
How does cryopreservation affect sperm?
Reduces number of surviving sperm and their competency - damages membranes Shortened lifespan - premature capacitation - so insemination must be accurate
133
What is vitrification?
Rapid cooling to avoid ice crystals, typically involving very high levels of cryoprotectants so sperm do not survive
134
What is a stem cell?
Relatively primitive cell that is capable of self renewal, potency and differentiation
135
Give 2 functions of stem cells in the body
Development and regeneration
136
Name 4 types of embryonic stem cell
Extraembryonic endoderm stem cells (XEN) Trophoblast stem cells (TS) Human naive embryonic stem cells (hESCs) Epiblast stem cells (EpiSCs)
137
Name 3 types of stem cell other than embryonic
Foetal stem cells Adult tissue specific stem cells Induced pluripotent stem cells
138
Give 4 applications of stem cells
Regenerative medicine, drug discovery, toxicology, disease modelling
139
How are human embryonic stem cells derived?
Blastocyst grown in IVF medium, immunosurgery with anti-trophectoderm antibodies and complement, inner cell mass isolated and cultured
140
What are 3 fates of stem cells?
Self renewal, differentiation, apoptosis
141
What can induced pluripotent cells be used for?
Can capture a specific genome from a population/disease and study effects Can test drugs on normal and affected phenotypes to see if they would be effective in specific populations
142
What are the 3 factors needed for successful stem cell treatment of disease?
Make desired cell, transplant it correctly and make sure it integrates
143
Name 5 ARTs for male factor infertility
IUI, ICSI, IVF, SSR, DI
144
What are the 2 types of pituitary suppression? What are the pros/cons?
GnRH agonists - may cause OHSS, longer and more expensive | GnRH antagonists - no initial flare up, shorter treatments, more flexibility and reversibility
145
How are follicles stimulated?
FSH daily injection given to stimulate oocyte growth
146
How is ovulation triggered? Is there a risk?
hCG injection when follicles are big enough - may have a risk of OHSS (or GnRH agonist if using an antagonist regime, less OHSS risk)
147
What is the preferred number of embryos transferred? When is this changed?
Single embryo transfer 2 transferred - if over 40 straightaway, if 37-39 only if there is not top quality embryos in 1st/2nd cycle (or always if 3rd cycle), and if under 37 transfer 2 on 3rd cycle and if on 2nd cycle there is not top quality embryos
148
What is luteal support?
Progesterone (or hCG) injections in the first few weeks to maintain pregnancy
149
Give 5 factors affecting IVF success
``` Age Cause of infertility Duration of infertility Number of previous attempts Other medical conditions Environmental factors Obesity ```
150
Explain the difference between action of GnRH agonists and antagonists and when they are given
GnRH agonists given continuously, suppressing gonadotrophins after an initial surge, then FSH stimulation performed and maturation triggered GnRH antagonists suppress gonadotrophins immediately, given after FSH stimulation and before maturation triggered

Embryo (1 decks)

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