Behavior Endo Exam 1

Earliest example of endocrine manipulation that pre-exists the field of behavioral endocrinology

Castration

Berthold’s Capon Experiment

Capons: Roosters that didn’t develop due to castration

• Typical male characteristics and behaviors altered due to removal of testes

• Reimplanting or transplanting of testes led to male development → gonads produce the necessary hormones for development

Hormone

A chemical signals released by endocrine glands into the bloodstream

• Acts on target organs/ tissue

• Regulate and control bodily functions

Neuro-Messengers

• Neurotransmitter: A chemical messenger that acts across the neural synapse

• Neuromodulator: a hormone that changes the response of a neuron to some other factors

• Neurohormone: a hormone produced by a neuron

• Neuropeptide: a peptide hormone produced by a neuron

• Neurosteroid: a steroid hormone produced by a neuron

Chemical Communication

• Intracrine

  • Chemicals regulate intracellular events (within the cell)

• Autocrine

  • Cell releases chemicals that feedback that influence self

• Paracrine

  • Secrete chemicals that affect adjacent cells

• Endocrine

  • Cells secrete chemicals into the bloodstream

• Ectocrine

  • Cells release substances into the environment to communicate with others

Allomones

Chemical messengers released by members of one species to
influence the behavior of members of another species

• Can mimic pheromones produced by recipient

  • flowers attract pollinators with scent

  • skunks spray repellant to ward off predators

Pheromones

Chemical messengers released by members of a species meant to influence the behavior of members of the same species

• Fhlemen response: animal curls back upper lip and lifts head to better inhale scent

Endocrine System

Organs: Hypothalamus, Pineal, Pituitary, Thyroid, Adrenal, Pancreas, Gonads (ovaries/ testes)

• Endocrine Glands are ductless

• Have rich supply of blood

  • Can travel anywhere in the body and interact with cells with appropriate receptor

Exocrine System

• Exocrine Glands have tubes or ducts where they release their products (can be internal or external)

  • ex: salivary, sweat, and mammary glands

Major Vertebrate Hormones

4 Major classes of Hormones secreted by the endocrine glands

• Protein and peptide hormones

• Steroid hormones

• Monoamines

• Lipid-based hormones

Most endocrine glands only produce a single class of hormone

Protein and Peptide Hormones

• Made up of amino acid building blocks

• Water–soluble (dissolves in blood, but cannot pass membrane)

• Receptors are found embedded in the cell membrane (require intracellular 2nd messenger)

• Vary in structure between vertebrates

  • Insulin, LH, FSH, oxytocin,

Steroid Hormones

• Precursor to all vertebrate steroid hormones is cholesterol

• Fat-soluble (passes membrane)

• Receptors are inside the cell and migrate to nucleus once bound (intrinsic enzymatic activity)

• Structures are virtually identical among vertebrates

• Glucocorticoids, androgens and estrogens

Monoamine

Derived from a single amino acid

• Epinephrine (adrenaline) and norepinephrine (noradrenaline) are derived from tyrosine

• Melatonin and serotonin are derived from tryptophan

Lipid-Based Hormones

Synthesized from essential fatty acids

• non-soluble in water

• diffuse through membrane

Hypothalamus

• Located at the base of the brain

• Links nervous system to endocrine system and controls pituitary gland

  • gonadotropin-releasing hormone (GnRH): signals anterior pituitary to release FSH - triggers start of reproduction, sexual maturity, and fertility

Pituitary

• Located below Hypothalamus → 2 glands fused as 1

  • Anterior Pituitary: produce protein hormone

    • Hypothalamus communicates directly through neurohormones

    • Luteinizing hormone (LH): sexual development, puberty, and reproductive function

    • Follicle-stimulating hormone (FSH): targets reproductive glands to control fertility/ development

  • Posterior Pituitary: Acts as a reservoir for neurohormones produced by the hypothalamus

    • Hypothalamus secretes neurohormones into blood vessels and enter general circulation

    • Oxytocin: birth in mammals (uterine contractions) and milk let down

Endocrine Axes

Complex network of interactions between glands, hormones, and the feedback mechanism

• HPA (hypothalamus-pituitary-adrenal): controls stress and daily energy

• HPG (hypothalamus-pituitary-gonadal): controls, development, reproduction, and age

• HPT (hypothalamus-pituitary-thyroid): controls metabolism

Thyroid

• Located in neck (upper trachea)

• Hormones are derived from single aa tyrosine and fat soluble

  • Parathyroid Hormone: elevates blood calcium

• Hypothyroidism: low level of iodine causes slow metabolism and fatigue

• Hyperthyroidism: very fast metabolism, high blood pressure, sleeping problems

Pancreas

• Located in the posterior abdomen

• Endocrine and exocrine functions

  • Insulin: only known hormone that can lower blood sugar

  • Glucagon: stimulates the breakdown of stored glycogen (acts in opposition to insulin)

Diabetes

Type 1: Body cannot produce insulin to regulate glucose

Type 2: Body becomes resistant to insulin levels

Adrenal Glands

• Located on top of kidneys → made of 2 distinct organs

  • Inner adrenal cortex:

    • '“adrenaline” epinephrine: “fight or flight” response

    • norepinephrine: stabilize blood pressure during high stress, focus, aid in “fight or flight”

  • Outer adrenal cortex: produces glucocorticoids [cortisol] (reduce inflammation, suppress immune system)

Pineal Gland

• Located within the brain

• Extremely variable in vertebrates

  • Mammals exclusively secretory gland, but for others can serve as photoreceptor (light cues for seasonal behavior and circadian rhythms)

  • Produce melatonin: controls sleep-wake cycle

Gonads

1) Production of gametes

2) Production of hormones (primarily steroid)

Testes

• Located varies (external for most mammals, for others abdomen)

• Primarily produce testosterone (androgen= sex hormones that trigger male physical traits)

Ovaries

• Located in the abdomen

• Estrogen: controls menstrual cycle

• Progesterone: prepares uterine lining for fertilization

3 Ways Mammals give Birth

Placental Mammals (Humans)

• Placenta is a blood rich tissue that attaches to uterus and gives nutrient to fetus

• Spend longer in the womb

Marsupials (Kangroo)

• Babies are still too young when born, must continue development in their mom’s pouch

Montremes (Platypus)

• One hole for reproduction, excretion, and laying eggs

• Lay eggs instead of giving birth

• Babies suck milk from pores

Ablation

Removal of the source of hormone

• Earliest method to study hormones

  • surgical remove suspect gland,

  • observe effects of removal,

  • supplement by reimplanting or injecting hormone,

  • observe effects of replacement

Bioassay

Test of the effects of the hormone on a living animal or living tissue

• Can measure unknown levels of hormone by using the hormone

  • Use a purified hormone create a dose-response curve and estimate level of same hormone in unknown dose sample

• Contaminants in sample may interfere with results from graph

  • Animal response may not be exclusively from said hormone

Friedmen Test

Developed a bioassay pregnancy test that was commonly used until 1950s

• Would inject a woman’s urine into an immature rabbit → pregnant woman’s hormones would cause rabbit to mature and ovulate

• Rabbis would have to be cut open to see results

Immunoassays

Measures hormone concentrations via binding of antibody to its antigen

• modern home pregnancy tests detect hCG levels in urine → 1st pregnancy test made by Margaret Crane

Immunocytochemistry

Uses antibodies to determine the location of a hormone in the body

• Antibodies labeled with marker molecules (like fluorescent dye) are introduced into dissected tissue

• Areas that become dyed have hormone present (often examined under fluorescent microscope)

Methods for Living Subjects

• PET: gives detailed measurements of real-time functioning of specific brain areas of people who are awake and alert

• fMRI

• Bioassays

Primary Antibody

Produced against antigen (e.g., hormone) by
immunizing animal with antigen

Secondary Antibody

Antibody made from a primary antibody of another species. The primary antibody was made from an antigen introduced to the species.

Epitope

Localized regions on the surface of an antigen that the
antibody binds to (particularly relevant term for protein hormones)

Polyclonal antibodies

Produced by injecting animal with antigen and collecting immune serum (antisera contains a variety of antibodies that react to antigen)

• less specificity (bind to multiple epitopes)

• Higher sensitivity

• Higher cross-reactivity

Monoclonal antibodies

Produced by injecting animal with antigen and cloning individual antibody cells to continue to produce one specific antibody

• Highly specific (bind to 1 epitope)

• Lower sensitivity

• Lower cross-reactivity

How are standard curve developed/ used for immunoassays?

Developed by testing known hormone concentrations, measuring signals, and plot a graph to create standard curve

• can compare levels in unknown sample

Use known hormone concentrations to find the unknown concentration in a sample.

Immunoassay vs. Bioassay

Bioassay: measure biological response to hormone to determine how much is present

• Give an animal/tissue known hormone concentrations → measure biological response → make standard curve → compare unknown sample's response

Immunoassay: measures antigen-antibody response to detect and measure hormone sample

• Make antibodies against the hormone → test known hormone concentrations with the antibodies → make standard curve → test unknown sample with antibodies → compare

Why must immunoassays be validated?

Validation = proving the assay measures what you think it measures.

To ensure the assay accurately measures the hormone and isn’t affected by sample substances.

• Biological validation: hormone measurement should match the animal’s actual hormonal response (biological sense)

Why sex?

In the beginning asexual reproduction was most common

• “Red Queen Hypothesis”

  • species must constantly adapt and evolve in order to survive when pitted against ever-evolving opposing species

Sexes defined

Different gamete sizes= anisogamy

• The sex producing the larger gamete/ova = female

• The sex producing the smaller gamete/sperm = male

Genetic Sex Determination

Predetermined

• Homogametic sex = two similarly shaped sex chromosomes

  • male birds and human females

• Heterogametic sex = two differently shaped sex chromosomes

  • female birds and human males

Gonochorism

• sexual system where there are 2 sexes, and individuals
  are typically either male or female (this is fixed)

Parthenogenesis

asexual reproduction in vertebrate w/o males

(exclusively females)

2 types of Hermaphroditism

Synchronous hermaphroditism: individuals have the sex organs of both
sexes and can produce both gamete types

Sequential hermaphroditism = individuals can change sex over the
course of their lifetime

Male Sexual Differentiation

1) SRY gene (on Y) → testis determination factor → germinal ridge develops into a testis

2) Formation of testes → secrete androgens (testostrone) → develop accessory organs = Wolffian duct develop, Mullerian duct system regress

• Testostrone: Wolffian develop

  • 5∝ enzyme converts testostrone into DHT → Male external genitalia

• Mullerian inhibitory hormone (MIH): needed regress Mullerian

3) External Male genitalia

Female Sexual Differentation

1) No SRY gene → germinal ridge develops into ovaries

2) Formation of Ovaries → secrete progesterone/ estrogen → develop Mullerian duct system, Wolffian duct regress

3) External female genitalia

**Mullerian duct develops in presence of ovaries or lack of gonads!

Why is there are no true hermaphrodite among humans or avian species?

Humans and birds are not capable of producing two gametes at once (Gonochorism) so cannot be hermaphrodite

Why is female development considered the default?

• Ovaries will develop from the geminal ridge if there is no SRY gene present

• MIH needed to stop Mullerian Duct (female accessory) to stop developing

Turner Syndrome

Congenital lack or damage to second sex chromosome (i.e., X0
individuals)

Characterized as female at birth
• Ovaries (but usually underdeveloped), internal and external accessory sex organs are
female
• Ovaries don’t produce steroid hormones → individuals treated with HRT to induce puberty

SRY and DSD (Differences of Sex Development)

SRY gene presence or absence can cause differences in sexual development for XX or XY

XX + SRY

XY + non-functional SRY

Why more DSD in Males

• Male development requires more steps/ hormonal signals which can create more opportunities for variation

Congenital Adrenal Hyperplasia

Congenital adrenal hyperplasia (CAH) is a condition where the fetal adrenal glands produce unusually high levels of androgens instead of enough cortisol.

Effect: In XX individuals, the extra androgens can cause masculinization of the external genitalia during development → larger clit

1 condition that is due to the lack of a specific enzyme

5α-reductase deficiency → ↓ conversion of testosterone to DHT → incomplete male external genital development in XY individuals.

Case of David Reimer

Proving that gender identity is not learned.

• Born w/ typical male characteristics, but botched circumcision → made into female presenting (testes removed)

• Was not AWARE he was born male

• Not Intersex or transgender → chose to retransition into male

• Proves that there is a genetic component to gender identity

Organizational Effects vs. Activational Effects

Organizational: early life critical components where hormones have permanent effect on the brain

Activational: hormones that affect behavior in puberty and adulthood → can be turned on and off