Pheromones

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Pheromones
Neurotransmitters
Other Cellular Regulators- Act like hormones
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Other Cellular Regulators Besides well recognized
kinds of hormone, other substances play important
roles as chemical messengers Ca Glucose-specif
ic stimuli for insulin secretion from the b cells
of the pancreas. Amino acids None of these
effectors are not TRADITIONAL hormones, but act
like hormones.

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Besides classics NTs Pheromones Glucose Calcium

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• Control of Endocrine Activity
• The physiologic effects of hormones depend
  largely on their concentration in blood and
  extracellular fluid. Almost inevitably, disease
  results when hormone concentrations are either
  too high or too low, and precise control over
  circulating concentrations of hormones is
  therefore crucial. The concentration of hormone
  as seen by target cells is determined by three
  factors
• 1.Rate of production
• 2.Rate of delivery
• 3.Rate of degradation and elimination

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• Control of Endocrine Activity
• Hormone as seen by target cells is determined
  by 3 factors
• Rate of production Synthesis and secretion of
  hormones are the most highly regulated aspect of
  endocrine control. Such control is mediated by
  positive and negative feedback circuits.
• Rate of delivery An example of this effect is
  blood flow to a target organ or group of target
  cells - high blood flow delivers more hormone
  than low blood flow.
• Rate of degradation and elimination Hormones
  have characteristic rates of decay, and are
  metabolized and excreted from the body via
  several routes. Shutting off secretion of a
  hormone that has a very short halflife causes
  circulating hormone concentration to plummet, but
  if a hormone's biological halflife is long,
  effective concentrations persist for some time
  after secretion ceases.

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Hormone Synthesis Diversity of hormones
structures Lots of interesting pathways of
biosynthesis Simplest of hormones-amino
acids Glycine and glutamate -act as NTs in
brain F and Y-are precursors of dopamine, NE and
Epi Which also function as NTs

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Hormone Synthesis Y also substrate for
generation of thyroid hormones W is precursor
for serotonin, a CNS NT and melatonin, a pineal
hormone

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Hormone Synthesis Peptide Hormones -translated
on secretory pathway (ER..golgi. Sec ves) Made
in RER Can have continuous or regulated secretion

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Hormone Synthesis Steroid Hormones Made within
the SER Steroid secreting cells easily recognized
by large amounts of SER Complex multiple enzyme
system for synthesis secretion

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Hormone Synthesis Thyroid Hormones Made on
protienaceous substrates outside the
cell Thyroglobulin Then taken up via endocytosis
into the thyroid gland-released from carrier
protein prior to secretion from thyroid. UNIQUE
PROCESS

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Hormone Synthesis Prohormones Result from
cleavage events after translation Even have
preprohormones Examples Renin (enzyme from
Kidney) Acts on angiotensinogen (substrate from
liver) Results in ANGIOTENSIN I which is
converted by another enzyme to Antgiotensin II

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Hormone Synthesis Prohormones Angiotensin II
and bradykins are examples of hormones that are
released from liver cells as larger prohormones
and converted to active hormone in the blood.

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Hormone Synthesis NTs Made in axon end of
neurons Neuropeptides like oxytocin and
vasopressin also made in neurons

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Hormone Synthesis Summary Variety of processes
and intracellular locations involved SER, RER,
Cholesterol from inside and outside the
cell, Secretory pathway involved in hormone
modifications, particulary glycosylation

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Control of Hormone Secretion Most hormones are
made within cells are packaged in secretory
vesicles until released Except thyroid and
steroid hormones Which are not in secretory
vesicles

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Control of Hormone Secretion Internal and
external effectors Extrinsic-light, sounds,
smell, temp, Etc. Stimulation of hormone
secreting cells results in vesicle fusion with
the PM and exocytosis of secretory granules

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Control of Hormone Secretion

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Control of Hormone Secretion Hormones often
stimulate secretion of hormones from other
endocrine glands Pit hormones TSH, FSH, LH and
ACTH simulate target tissue cells of thyroid,
adrenal, gonads to secrete their own
hormones Hormones control other hormones Cascade
effect

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Control of Hormone Secretion Neuroendocrine
transduction stimulation of hormone secretion by
nerves

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Control of Hormone Secretion Hormone interaction
with some membrane receptors results in membrane
depolarization -stimulates movement of Cainto
cells which results in sec. vesicle
exocytosis Some chemical messenger inhibit
secretion by resulting hyper polarization

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Hormone Delivery-several routes Endocrine,
Para, auto neurocrine- neuron contact target
cell and releases hormone neuroendocrine-neuron
to blood lumonal-released into lumen of the
gut Some delivered by all multiple routes

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Hormone Circulation and metabolism Peptide
hormones have short half lives Exopeptidases and
endopeptidases Most steroid hormones bound to
plasma proteins. Steroid hormones much more stable

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• Feedback Control of Hormone Production
• Feedback circuits
• are at the root of most control mechanisms in
  physiology,
• and are particularly prominent in the endocrine
  system.
• Instances of positive feedback certainly occur,
  but negative feedback is much more common.

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• Feedback Control of Hormone Production
• Negative feedback is seen when the output of a
  pathway inhibits inputs to the pathway.

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• Feedback loops are used extensively to regulate
  secretion of hormones
• An important negative feedback loop is seen in
  control of thyroid hormone secretion.
• The thyroid hormones thyroxine and
  triiodothyronine ("T4 and T3") are synthesized
  and secreted by thyroid glands and affect
  metabolism throughout the body.

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• The basic mechanisms for control in this system
  (illustrated on next slide) are
• 1.Neurons in the hypothalamus secrete thyroid
  releasing hormone (TRH), which stimulates cells
  in the anterior pituitary to secrete
  thyroid-stimulating hormone (TSH).
• 2. TSH binds to receptors on epithelial cells in
  the thyroid gland, stimulating synthesis and
  secretion of thyroid hormones, which affect
  probably all cells in the body.
• 3.When blood concentrations of thyroid hormones
  increase above a certain threshold, TRH-secreting
  neurons in the hypothalamus are inhibited and
  stop secreting TRH. This is an example of
  "negative feedback".

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Inhibition of TRH secretion leads to shut-off of
TSH secretion, which leads to shut-off of thyroid
hormone secretion. As thyroid hormone levels
decay below the threshold, negative feedback is
relieved, TRH secretion starts again, leading to
TSH secretion ...

-

-
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Target cell response TRH receptors only found in
anterior pituitary TSH receptors only found in
thyroid gland TH receptors found on every
cell Cascade effect

-

-
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• Another type of feedback is seen in endocrine
  systems that regulate concentrations of blood
  components such as glucose.
• Drink a glass of milk or eat a candy bar and the
  following (simplified) series of events will
  occur
• Glucose from the ingested lactose or sucrose is
  absorbed in the intestine and the level of
  glucose in blood rises.
• Elevation of blood glucose concentration
  stimulates endocrine cells in the pancreas to
  release insulin.
• Insulin has the major effect of facilitating
  entry of glucose into many cells of the body - as
  a result, blood glucose levels fall.
• When the level of blood glucose falls
  sufficiently, the stimulus for insulin release
  disappears and insulin is no longer secreted.
• Numerous other examples of specific endocrine
  feedback circuits will be presented in the
  sections on specific hormones or endocrine
  organs.

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• Hormone Profiles Concentrations Over Time
• One important consequence of the feedback
  controls that govern hormone concentrations and
  the fact that hormones have a limited lifespan or
  half-life is that most hormones are secreted in
  "pulses". The following graph depicts
  concentrations of luteinizing hormone in the
  blood of a female dog over a period of 8 hours,
  with samples collected every 15 minutes

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• The pulsatile nature of LH secretion in this
  animal is evident.
• LH is secreted from the anterior pituitary and
  critically involved in reproductive function the
  frequency and amplitude of pulses are quite
  different at different stages of the reproductive
  cycle.
• With reference to clinical endocrinology,
  examination of the graph should also demonstrate
  the caution necessary in interpreting endocrine
  data based on isolated samples.
• -

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• A pulsatile pattern of secretion is seen for
  virtually all hormones, with variations in pulse
  characteristics that reflect specific physiologic
  states.
• In addition to the short-term pulses, longer-term
  temporal oscillations or endocrine rhythms are
  also commonly observed and undoubtedly important
  in both normal and pathologic states.

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• Mechanisms of Hormone Action
• Immediately after discovery of a new hormone, a
  majority of effort is devoted to delineating its
  sites of synthesis and target cells, and in
  characterizing the myriad of physiologic
  responses it invokes.
• An equally important area of study is to
  determine precisely how the hormone acts to
  change the physiologic state of its target cells
  - its mechanism of action.

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• Mechanisms of Hormone Action
• Understanding mechanism of action is itself a
  broad task, encompassing structure and function
  of the receptor, how the bound receptor
  transduces a signal inside the cell and the end
  effectors of that signal. This information is not
  only of great interest to basic science, but
  critical to understanding and treating diseases
  of the endocrine system, and in using hormones as
  drugs.

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Physiological roles of Hormones What do hormones
do???

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Physiological roles of Hormones Hormones control
activity of all cells in the body Affect
cellular synthesis and secretion of other
hormones After metabolic processes (catabolic
and anabolic). Turnover of sugar, proteins and
fats Affect Contraction, relaxation and
metabolism of Muscle

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Physiological roles of Hormones Reproduction Cell
growth and proliferation Excretion and
reabsoroption of ions Affect action of other
hormones Role in animal behavior

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Physiological roles of Hormones Some hormones
only exist a few times in the life of an
individual hCG Sometimes still have hormone but
not sensitive to it any longer Sometimes no
longer produce hormone-thyroid hormone, estrogen

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General mechanisms of Hormone action Receptors S
econd messengers Phosphorylation involves
STY Kinases and phosphatases

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Reminder aboutGeneral mechanisms of Hormone
action Steroid hormones have intracellular
receptors. So do Thyroid hormones

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Endocrine pathophysiology Failure of a gland to
secrete enough hormone can lead to fatal
consequences No insulin-hyperglycemia-coma and
death if untreated

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General mechanisms of hormone action Hormones
regulate specific target tissues NOT ALL CELLS IN
the body Determined by?? Receptors-proteins bind
hormones Contribute to specificity of
action Can be PM or cytosolic or nuclear

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Hormone response effected by Receptor Levels and
hormone levels Oxy and vasopressin AVP have
similar structure and both hormones stimulate
uterine smooth muscle contraction and activate
renal cAMP Uterine receptors more sensitive to
OXY Renal receptor more sensitive to AVP Normal
hormone conc. Each hormone only activate
appropriate cell type

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Hormone response effected by Receptor Levels and
hormone levels When one hormone binds to the
receptor of another hormone, this is called CROSS
TALK Happens with lots of hormones. If hormone
levels are high, will not only act on its own
receptor, but similar hormone receptors

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Some hormones stimulate a number of
tissues. Insulin stimulates glucose uptake into
skeletal muscle and Fat cells But also talks to
liver to shut down output of glucose from
liver High Insulin receptor levels on fat, muscle
and liver, but low levels in other tissues.

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Insulin receptors at high levels in skeletal
muscle Fat cells LIVER Cells where INSULIN
MODULATES glucose metabolism

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Insulin receptors at low levels in all other
tissues where this hormone only has a modest
effect on GROWTH DOES NOT MODULATE GLUCOSE
METABOLISM IN THESE OTHER TISSUES

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RECEPTORS FOR A PARTICULAR HORMONE ARE ONLY
EXPRESSED IN CELLS WHERE THE HORMONE ACTS. MORE
ACTION-MORE RECEPTORS UNDERSTAND INSULIN
EXAMPLE (IT IS AN EASY ONE)

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Hormone response effected by Receptor Levels and
hormone levels Have high levels of receptor in
tissue that are primary responders

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Hormones act via own receptors at normal
concentrations At high hormone concentrations,
hormones can act on similar receptors NE and
Epi Oxy and vaso IGF-1 and insulin

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In most cases, a maximum biological response to a
hormone is achieved when only a small of the
receptors are occupied. WHY?

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Agonists and Antagonists Exocrine Endocrine,
Paracrine, Autocrine Secretin Humoral Development
origin of hormone Homeostasis pH ___
Temp___C If you secrete one, then you secrete
many..
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Endocrine Activity-rate of production,
delivery, and degradation Steroid hormones, made
in SER Thyroid hormones-outside of cell Not
Secreted in vesicles like peptide
hormones Feedback circuits
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• Contribute to complexity of Hormone Action
• Pulsatile secretion

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General mechanisms of Hormone action Receptors S
econd messengers Kinases and phosphatases CROSS
talk

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Hormones are complex Lots of things to be
studied regarding hormones Methods are used to
perform ENDOCRINOLOGY EXPERIMENTS?

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• General considerations
• Source
• Structure determination
• Biosynthesis
• Control of secretion
• Cellular mechanism of secretion
• Circulation and metabolism
• Biological actions/functions
• Mechanisms of action

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Scientific Method observation experiments
formulate hypotheses Must be testable via
observation or experimentation Lot of Data
Theory Theory accepted Law of
Principle or DOGMA
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Always need a control vehicle if using
solution Sham operation if doing surgery Always
limit variables
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Show specificity
Effects Usually Time and Dose Dependent
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Old principle of Logic Occams razor of several
reasonable explanations. The simplest is most
probable.
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Types of Experiments in Endocrinology
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Chemical ID 10 -amino acid sequence

20 secondary
30 R group interactions
40 association with other proteins
Modifications like glycosylation, phosphorylation
and sulfation
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Methods of Endocrine Analysis Microscopy (light,
EM to whole-body scanning techniques (CAT, PET,
MRI)
Imaging studies are important component of
endocrinology studies
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Imaging also important component of diagnosis and
treatment
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The picture shows a tumor cell disintegrating
after an attack by a T cell.  Two additional,
intact tumor cells are shown in. The successful
cytotoxic T lymphocyte may now make these cells
its targets.
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Bioassays Different approaches to examine
hormone activity Based on activity
(enzymatic) Or association with another molecule

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Structure-Activity Studies Mutate part of the
gene or one base of the gene to determine if that
part is important in hormone activity and
function Site directed mutagenesis

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Site directed mutagenesis

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Histological and cytological studies Hypertrophi
c-enlarged This means bigger cells Contain more
ER and Golgi Opposite of atrophic Hyperplasia or
Hyperplastic An increase in number

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Enlarged spleen cells
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Enlarged fat cells at top
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Hypertrophic-enlarged This means bigger
cells Contain more ER and Golgi Opposite of
atrophic
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Hyperplasia or Hyperplastic An increase in number
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Can have Hypertrophy or Hyperplasia or both
depending on condition

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Immunocytochemistry This is method to examine
peptide or peptide hormone in a tissue. Must have
an antibody against that protein. Antibody bind
hormone (protein). Use Fluorescent dye to bind
antibody to visualize location of protein.

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Immunocytochemistry to show marker of Hodgkins
lymphoma
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Immunocytochemistry to two proteins
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Immunocytochemistry This is method CAN ALSO BE
used to determine what tissue produces a hormone
and/or where in the cell it is localized

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Radioisotope Studies I125 take up by
thyroid Radioactive Ca measured P to perform
phosphorylation studies Half life studies Kinase
studies

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Radioisotope Studies I125 take up by
thyroid the amount of iodide the thyroid absorbs
is a reliable indicator of how much hormone the
gland is producing

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Surgical Methods Endocrine organs can be
transplanted to a new location Ectopic-abnormal
site Hypophysectomy-removal of
pituitary Pituitary target organs become atrophic

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Ectopic-abnormal site
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Removal of both members of paired (bilateral
roans) such as adrenals or gonads usually leads
to COMPLETE loss of dependent tissue/organ FUNCTIO
N. Only unilateral (one) removal Have
compensatory hypertrophy To account for ablated
organ

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Parabiosis Animals are sutured together and share
vascular systems Remove endocrine gland of one
mouse, the organs of other animal will
hypertrophy. Chemical communication between
animals
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Obese gene-genetic defect in this gene causes
obesity and type II diabetes The obesity gene
codes for a hormone called leptin that is made
exclusively in FAT

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diabetes gene-genetic defect in this gene causes
obesity and type II diabetes The diabetes gene
codes for the leptin receptor which is primarily
expressed in the hypothalamus

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Ob/ob mice-no leptin db/db-no
leptin receptor 2 commonly used rodent models of
type II diabetes
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Parabiosis of ob/ob and db/db mice Ob/ob mice-no
leptin db/db-no leptin receptor

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Gray mouse is wild type

Ob mouse and wild type-get leaner ob mouse.
Sharing Hormone
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db mouse and wild type-db does not get leaner
because of defective receptor, not a problem with
the hormone.
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db mouse and ob mouse-ob mouse gets better as it
gets circulating hormone from db mouse. Db mouse
does not improve because of defective receptor
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This pivotal parabiosis experiment showed that ob
gene coded for circulating factor and that db did
not.
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Positional cloning is method to identify and
clone the gene that creates a phenotype.
So-finding the genotype

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Positional cloning is method to identify and
clone the gene that creates a phenotype.
So-finding the genotype Obese mice-defect in
obese gene Took over 10 years to find gene Same
with diabetes gene

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Obese mice-defect in obese gene Found was fat
specific
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RIA Detection of hormones at minute
concentrations. Need an antibody

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(No Transcript)
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RIA Detection of hormones at minute
concentrations. Need an antibody

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RIA Nobel Prize in Medicine (1977) to Rosalyn
Yalow

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RIA At first was only useful for petptides.
Now possible to trick antibody producing cells
to make specific anitbodies against all type of
chemical substances Can measure Steroid and
Thyroid hormones now with this assay

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Electrophysiology membrane potential

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Electrophysiology The cell-attached patch clamp
uses a micropipette attached to the cell membrane
to allow recording from a single ion channel.
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"Current Clamp" is a common technique in
electrophysiology. This is a whole-cell current
clamp recording of a neuron firing due to it
being depolarized by current injection
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Chemicals Alloxan or streptozoticn destroy
islets which produce insulin-induce Type I
diabetes in an animal Cobalt chloride destroy
glucagon secreting cells Induce diabetes
chemically or surgically

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Hormone Replacement Therapy (HRT) Reverse the
undesirable effects of hormone loss following
surgery or disease state or age. Children
lacking GH are given this hormone to avoid
stunted growth

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Immunological Neutralization of Hormone activity
Antibodies against a hormone injected. Bind
hormone and inhibit its action Mostly used as
Experimental rather than treatment approach to
understand the actions of specific
hormones Inject anti-NGF antibodies no growth
and devt of SNS

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Pharmacological experiments Actinomycin
D-inhibits transcription Cycloheximide-inhibits
translation Colchicine-disrupt microtubules Cytoch
alasin B-disrupts microfilament

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Pharmacological experiments Actinomycin D and
Cycloheximide Can be used to determine if an
action of a hormone is genomic

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Specific Example To determine if effect of a
hormone is dependent on new proteins synthesis,
treat target cells with CH then look at hormone
action. If action is blocked, know the effect
is genomic

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Pharmacological experiments Colchicine and
Cytochalasin can be used to tell if signaling or
secretion is dependent on cytoskeleton

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Tissue Extracts and purification Type I diabetics
need daily injections of insulin Used to come
from pigs, cattle, horse. Slaughterhouse
blood Contaminants from animals Specificity
issues Insulin now made recombinant Sheep
melatonin Bovine GH

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Disadvantages of using hormones purified from
animals or Slaughterhouse blood -Contaminants
from animals -Specificity issues -Cost, much
cheaper to make recombinantly Sheep melatonin
Bovine GH

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Recombinant DNA methods Way in which we make
insulin Genetic engineering in various
species Fish, mice, rats.

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Transgenic Animals introduce gene in
animal -Usually replace wild type with a
mutant -Or express gene from a different
promoter.

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Transgenic Mice over expressing Tropomodulin Have
enlarged right atrium and ventricle and are larger

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Labeled for two different proteins which are
normally present in myofibrils. The alternating
bands of tropomodulin (green) and alpha-actinin
(red) show the dense packing of myofibril
throughout the interior of the cell.

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The normal alternating pattern of tropomodulin
and alpha-actinin immunoreactivity has been
disturbed. The yellow color indicates
colocalization of both red and green labels (an
abnormal distribution). Transgenic mice with this
level of tropomodulin overexpression suffer from
cardiomyopathy

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transgenic mice that overexpress TGFß1 in the
CNS animals developed severe hydrocephalus
transgenic colony serves as a model of
congenital hydrocephalus
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overexpress neurotrophin-3 (NT-3) in skeletal
muscle When lifted by the tail, wildtype extend
their hindlimbs and digits. In contrast, all
transgenic NT-3 mice retract their hindlimbs to
the body and clench their paws in a "clasping
phenotype"
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Transgenic mice has different coat color
Transgenic mice extremely useful in studying
diseases