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Endocrinology > Lecture 2 > Flashcards

Lecture 2 Flashcards

0
Q

Which mammalian hormones have feedback regulation of synthesis

A

Steroids
Thyroxine derivatives
Peptides and proteins
Catecholamines

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1
Q

Three major classes of human hormones

A

Protein and peptide hormones
Steroid hormones
Tyrosine derivatives

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2
Q

How long is storage of preformed steroid hormones

A

Very little

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3
Q

Storage of preformed thyroxine

A

Several weeks

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4
Q

Storage of peptide hormones

A

One day

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5
Q

Storage of catecholamines

A

Several days, in adrenal medulla

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6
Q

Mechanism of secretion, steroids

A

Diffusion through plasma membrane

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7
Q

Thyroxine mechanism of secretion

A

Proteolysis of thyroglobulin

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8
Q

Mechanism of secretion peptides

A

Exocytosis of storage vesicles

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9
Q

Mechanism of secretion catecholamines

A

Exocytosis of storage vesicles

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10
Q

Binding to plasma proteins - steroids

A

Yes

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11
Q

Binding to plasma proteins - thyroxine

A

Yes

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12
Q

Binding to plasma proteins - peptides

A

Rarely

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13
Q

Binding to plasma proteins- catecholamines

A

No

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14
Q

Lifetime in blood plasma - steroids

A

Hours

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15
Q

Lifetime in blood plasma-thyroxine

A

Days

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16
Q

Lifetime in blood plasma-peptides

A

Minutes

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17
Q

Lifetime in blood plasma- catecholamines

A

Seconds

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18
Q

Time course of action-steroids

A

Hours to days

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19
Q

Time course of action-thyroxine

A

Days

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20
Q

Time course of action-peptides and proteins

A

Minutes to hours

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21
Q

Time course of action-catecholamines

A

Seconds or less

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22
Q

Receptors -steroids

A

Cytosolic or nuclear

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23
Q

Receptors - thyroxine

A

Nuclear

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24
Q

Receptors - peptides and proteins

A

Plasma membrane

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25
Q

Receptors - catecholamines

A

Plasma membrane

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26
Q

Mechanism of action - steroids and thyroxine

A

Receptor-hormone complex controls

Transcription and stability of mRNAs

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27
Q

Mechanism of action - peptides

A

Hormone binding triggers synthesis of Cytosolic second messengers or protein kinase activity

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28
Q

Mechanism of action - catecholamines

A

Hormone binding causes change in membrane potential or triggers synthesis of Cytosolic second messengers

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29
Q

Two classes of hormone receptors

A

Intracellular

Cell surface

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30
Q

How does negative feedback system work

A

A product sends message back to source to cut back production

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31
Q

How does positive feedback loop work

A

Product sends message bsck to source to make more product

32
Q

How is parturition an example of a positive feedback loop

A

Posterior pituitary makes oxytocin, which produces uterine contraction, which creates a cervical stretch as baby’s head is pushed forward. Stretch sends positive feedback to posterior pituitary to make more oxytocin and to uterus to contract more

33
Q

How does two hormone feedback system work

A

As one increases, the other decreases and vice versa

34
Q

What controls activity of thyroid glands, adrenal cortex, and gonads

A

Feedback effects of their circulating hormones on the hypothalamic-pituitary axis

35
Q

What controls pancreas and parathyroid

A

Feedback signals of regulated variable

36
Q

Six experimental approaches used in endocrinology research

A 
Surgical approach
Parabyosis 
Immunological- immunolocalization and radioimmunoassay
Ligand receptor binding
Bioassay
Gene manipulation (molecular biology)
37
Q

Explain the Berthold experiment with roosters (concept of compensatory hypertrophy) surgical approach

A

Group I had both testes removed
Group II had one testis replaced
Group III had one testis exchanged

Results
I. comb and wattles small, no interest in hens, weak crow, listless fight behavior
II. Comb and wattles normal, interest in hens, normal crow, aggressive fight behavior, testis larger than in controls
III. Same as II

38
Q

Parabyosis

A

The joining of two individuals

39
Q

Example of Parabyosis experiment

A

Surgically achieved shared circulation in mice. Compensatory organ hypertrophy.

40
Q

Immunolocalization

A

Using immunologic techniques, including specific antibody, to identify location of molecules or structures within cells or tissues

41
Q

Radioimmunoassay

A

Technique for determining antibody levels by introducing an antigen labeled with a radioisotope and measuring the subsequent radioactivity of the antibody component

42
Q

Immunodeficiency assay

A

Antibodies immobilized into a plastic surface are used to capture the target antigen
Second antibody linked to enzyme is then added. It binds to a different location on target antigen.
Plate wells are washed to remove unbound components
Substrate is added
Enzymatic reaction is stopped in order to establish a consistent time period for all wells. After stopping, color is measured.
Color generated is directly proportional to the amount of analyze present.

43
Q

Concept of immunometric assay

A

Antigen specific antibody is attached to a solid-phase surface
Test specimen is added, which may or may not contain the antigen
An enzyme labeled antibody specific to the antigen is added
Chromogenic substrate is added, which in the presence of the enzyme, changes color.

44
Q

What is relationship between hormone binding and biological response when there are spare hormone receptors

A

The concentration of hormone can be smaller if there are spare receptos to achieve the same amount of binding as it would take with fewer receptors

45
Q

Amino acid derivatives that interact with cell surface receptors

A

Epinephrine and histamine

46
Q

Where does epinephrine originate? Major effects?

A

Adrenal medulla
Increase in pulse rate and blood pressure, contraction of most smooth muscles, glycogenolysis in liver and muscle, hydrolysis in adipose tissue

47
Q

Histamine origin and effects

A

Mast cells

Dilation of blood vessels

48
Q

Do prostaglandins react with cell surface receptors

A

Yes

49
Q

What are prostaglandins a derivative of

A

Arachnid panic acid

50
Q

Origins and major effects of prostaglandins

A

Most body cells

Contraction of smooth muscle

51
Q

Examples of peptide hormones that interact with cell surface receptors

A 
Follicle stimulating hormone (FSH)
Glucagon
Insulin
LH releasing hormone
Luteinizing hormone
52
Q

Source and effects of FSH

A

Anterior pituitary

Stimulates growth of oocyte and ovarian follicles and estrogen synthesis by follicles

53
Q

Sources and effects of glucagon

A

Pancreas alpha cells

Stimulates glucose synthesis and glycogen degradation in liver; lipid hydrolysis in adipose tissue

54
Q

Source and effects of insulin

A

Pancreas beta cells
Stimulates glucose uptake into fat and muscle cells; carbohydrate catabolism, stimulates lipid synthesis by adipose tissue; general stimulation of protein synthesis and cell proliferation

55
Q

Source and effects of LH releasing hormone

A

Hypothalamus, neurons

Induces secretion of LH by anterior pituitary

56
Q

LH source and effects

A

Anterior pituitary

Maturation of oocyte, stimulates estrogen and progesterone secretion by ovarian follicles

57
Q

Examples of peptide growth/differentiation factors that interact with cell surface receptors

A

Epidermal growth factor
Nerve growth factor
Platelet derived growth factor

58
Q

Source and effects of insulin like growth factor 1

A

Liver and other cells
Autocrine/paracrine growth factor induced by somatotropin; stimulates cell growth and division and glucose and amino acid uptake, increase in liver glycogen synthesis

59
Q

Nerve growth factor origin and effects

A

All tissues innervated by sympathetic neurons

Growth and differentiation of sensory and sympathetic neurons

60
Q

Platelet-derived growth factor origin and effects

A

Platelets and cells in many other tissues
Chemotaxis of connective tissue cells and inflammatory cells; development and survival of cells in the nervous system;wound healing

61
Q

What are the two types of cell surface receptors

A

Linked to TK

Linked to G proteins

62
Q

What are the two subgroups of receptors linked to TK

A

Growth factor receptors intrinsic TK

Cytokines receptors recruit TK

63
Q

Two types of subgroups of receptors linked to G proteins

A

Adenylate cyclase

PLC

64
Q

Two types of intracellular receptors

A

Class 1 Cytosolic

Class 2 nuclear

65
Q

Mechanism of action of G protein linked receptors

A
  1. Ligand binds with cell surface receptor
  2. Conformational change in receptor
  3. Receptor binds to G alpha protein
  4. Induces conformational change in G alpha
  5. GDP bound to G alpha is replaced by GTP and the subunit disassociates from Gbetagamma
  6. G alpha binds to adenylyl Cyclase and activates cAMP synthesis
  7. Hormone dissociates
  8. Hydrolysis of GTP to GDP causes G alpha to dissociate from adenylyl Cyclase and bind to Gbetagamma
66
Q

Five second messengers

A 
3',5'-cyclic AMP
3',5'- cyclic GMP
1,2- diacylglycerol
Inositol 1,4,5- triphosphate
Calcium ion
67
Q

What does binding of growth hormone do to receptor? What does it recruit?

A

Dimerization of receptor

Recruits cytoplasmic tyrosine kinase,JAK-2

68
Q

Where does JAK-2 bind in GH receptor

A

Juxta membrane region of intracellular domains of receptor, known as Box 1

69
Q

What does JAK-2 activate

A

MAPK

70
Q

What does JAK-2 phosphorylate

A

Tyrosines on STATs

They form dimers and undergo translocation into nucleus, where they act as transcriptional regulatory proteins

71
Q

How does GH rapid insulin-like metabolic effects

A

IRS-1 and IRS-2 are phosphorylated by JAK-2 and recruit p85 subunit of P13 kinase

72
Q

What is the structure of the insulin receptor

A

Disulfide bridges link the alpha subunits to one another and also to two identical beta subunits, which cross the plasma membrane.

73
Q

What does insulting binding to receptor result in?

A

Insulin binding to alpha subunits in auto phosphorylation of the intracellular domains of the beta subunits

74
Q

What does phosphorylation of insulin receptor beta subunits cause

A

Docking of IRS-1 or IRS-2, which can then be activated by tyrosine phosphorylation P

75
Q

How does MAPK pathway work in insulin receptor

A

Grb2 links IRs-1 to the GDP/GTP exchange protein, Sos. The Sos Grb2 complex gets near small G protein RAs, located in plasma membrane. This triggers RAs by the exchange of GTP for GDP.
Serine/threonine kinase enzyme Raf activates a tyrosine/serine/threonine kinase enzyme (MEK), which activates a multifunctional MAPK, which targets proteins located in multiple regions of cells

76
Q

What can MAPK modulate in insulin receptor

A

C-fos and c-junk and can also release arachidonic acid by the action of phospho lipase A2

77
Q

What do IRS1 or 2 activate via insulin receptor

A

The P13 kinase pathway which enhances glucose transport

78
Q

Mechanism of steroid hormone receptor

A

Serum binding protein transports steroid hormone to vicinity of membrane
Hormone diffuses through membrane
It bind with Cytosolic receptor
Enters nucleus and influences trancription
Mature MRNA exists nucleus and goes to ribosome complex, where it is translated into a protein

Endocrinology (21 decks)

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