Diff11 - 41 Flashcards
What are the three kinds of growth?
Hyperplasia, hypertrophy, accretion
Outline cell proliferation
Gap 1 - cell enlarges; Synthesis - DNA replication; G2 - end of interphase; Mitotic - cell actually divides
What controls the mechanics of cell proliferation?
Cyclins > cyclin dependent kinases > trigger proteins
Describe the status of fully differentiated cells
G0
Outline cell division in early drosophila
Syncytium - single cell, multiple nuclei; rapid synchronous cell cycles with only S and M phases; at 14th cycle, G2 is introduced, and cellularisation occurs; each cell acquires its own cell division rate - mitotic domains
What controls cell division in mitotic domains?
String - protein
Outline string expression
Maternal during 1st 13 divisions, zygotic after 13th
What delays certain mitotic domain mitosis?
Tribble - inhibitor of string
Characterise limb size
Intrinsic sizing - absolute dimensions, not number of cells
What determines the size of a structure?
No just rate of growth, but also duration
What determines the size of drosophila?
Size of larva - determined by insulin signaling which affects duration and rate of larval growth
What important mammalian factors determine growth patterns?
IGF1/2
What does IGF stand for?
Insulin-like growth factors
What controls post-embryonic mammalian growth?
Growth hormone
What mediates GH effects?
IGFs
Where is GH made?
Pituitary gland
What induce GH release?
GH releasing hormone
What inhibits GH release?
Somatostatin from the hypothalamus
How does GH feedback work?
GH promotes somatostatin and inhibits GHRH; GH promotes IGF1/2; GH promotes GHRH
What is an oncogene?
Activated proto oncogene - genes that if mutated lead to a loss of growth control
What is a suppressor gene?
Genes that normally inhibit growth - a loss of which leads to a loss of growth control
What are teratomas?
Similar to embryonic cells and can give rise to tissues from all three germ layers
What is another term for molting?
Ecdysis
What are intermolt stages called?
Instars
How many instars do drosophila undergo before pupation?
3
What is molting activated by?
Activation of stretch receptors, followed by release of protothoracicotropic hormone from the corpus alatum, which leads to the release of ecdyson from the protothoracic gland
Outline the influence of ecdyson
Cuticle separates from epidermis, freed epidermal cells proliferate, fluid barrier is secreted, new cuticle is secreted
What can influence metamorphosis?
Nutrition, temperature and light
What do external cues for metamorphosis affect internally?
Affect the relative levels of juvenile hormone and ecdysone
What is the role of juvenile hormone?
Prevention of metamorphosis
What is the role of ecdysone?
Promotion of metamorphosis
What two chemicals balance metamorphosis in frogs?
Prolactin (-) and thyroxine (+)
What is interesting about thyroxine?
Positively feeds back; has different effects on different limbs (generation of limbs, degeneration of tail)
What is senescence?
Age dependent decline in vital physiological functions
Give an example of wear and tear senescence
Feeding muscles in c.elegans
Give an example of genetically programmed senescence
Drosophila
What is the disposable soma theory?
Natural selection tunies life history of the organism so that sufficient resources are invested in maintaining the repair mechanisms that prevent aging at least until that organism has reproduced and cared for its young
What factors are thought to contribute to control of aging?
DNA damage and oxygen radicals, genetic mutations, binge eating
How does the c.elegans extend its life?
IGF signalling inhibits FOXO, which regulates increased resistance to stressors such as antimicrobial genes
How does binge eating affect life span?
Reduction in caloric intake can extend life span - possibly due to reduced reactive oxygen generation, possibly downregulation of IGF
What are sirtuins?
Protein deacetylases and are thought to be the target of resveratrol - compound from red wine!
