Exam 3- Block Flashcards
What are the main differences in the characteristics for benign and cancerous (malignant) tumors?
Malignant tumors are characterized by uncontrolled growth, invasion of local tissues and it can metastasize.
Benign tumors have uncontrolled growth only
What are three general ways in which cancer can be induced?
Chemical carcinogens
Irradiation
Viruses
Name 5 chemical carcinogens.
Alkylating agents Polycyclic aromatics Aromatic amines Nitrosamines Natural compounds such as aflatoxin B1 Inorganic materials such as arsenic, asbestos, beryllium, cadmium, and chromium
Direct carcinogen
Direct: act directly on a molecule
Pro-carcinogen
Pro-carcinogen: must be activated by prior metabolism
Proximate carcinogen
Proximate carcinogen: intermediate compounds along the activation route
Ultimate carcinogen
Ultimate carcinogen: the final compound along the activation route
Promoter
A compound required to carry the carcinogenic process through to the next stage to produce malignant tumors
Common: saccharin and phenobarbital
Initiators
Something that modifies DNA in order to produce a mutation leading to cancer
Point mutations
One base pair replaces another
Transition
One purine/pyramidine replaces another
Purines: adenine, guanine, hypoxanthine, xanthine
Pyrimidine: cytosine, thymine, uracil
Transversion
One purine replaces a Pyrimidine (or vice-versa)
Insertion/deletion mutations
A mutation where one or more nt base pairs inserted into or removed from DNA
Ames test
A test to screen for possible carcinogenic compounds by observing whether they cause mutations in sample bacteria
Strain of salmonella tryphimirium which cannot make histidine and lacks LPS coat that makes it impermeable to many compounds is placed on a culture plate without histidine in the medium. Suspected mutagen placed onto medium. If some bacteria mutate back to his+ phenotype in 2 days, number of colonies gives a mutagenesis score.
Approximately what percentages of cancers are caused by viruses and chemical carcinogens?
80% of non-skin cancers come from chemicals. 15% of non-skin cancer come from viruses
What are 4 major human tumor viruses and what types of cancer do they induce? And 1 bacterial
Epstein-Barr: Burkitt’s lymphoma, B cell lymphomas, and nasopharyngeal Cancer
Hep-B virus: hepatocellular carcinoma
Human papillomaviruses: genital tumors
Lymphoma virus-1: Human T-cell leukemia
H pylori: mucosal associated lymphoid tissue (MALT) lymphomas - gastric cancers
What are the 4 genes on the Rous Sarcoma virus, and what do they code for?
Gag: for core protein
Pol: for reverse transcriptase
Env: for envelope protein
V-src (viral sarcoma)- mediates host cell transformation (oncogene!)
What are the stages of the cell division cycle for eukaryotic somatic cells?
G1- gap (or growth) phase S- DNA synthesis phase G2- 2nd gap phase M- mitosis phase G0- quiescent phase
Interphase : time from mitosis to next mitosis
R: restriction point near end of G1
In general terms, what are some of the things that cells must do in order to reproduce?
- Increase in size
- Synthesize proteins, DNA, RNA, and organelles
- Form and segregate new chromosomes
- Control and surveil this process carefully
- Produce daughter cells
The formation, activation, and deactivation of what compounds exert major control over cell cycle?
Specific protein kinases (or CDK’s)
Cyclins, the protein regulators of the protein kinases
Kinase inhibitors
Specific phosphoprotein phosphatase
What are two key timing decisions that are made as the cell cycle progresses?
When to enter S phase
When to enter mitosis
What are cyclins, and what do they control? About how many are known?
Cyclins exert control in when the cell can enter mitosis after DNA synthesis and major architectural changes have completed.
They play a major role in changes in cell architecture during the cell cycle. These include the breakdown of the nuclear envelope, the condensation of chromatin, and extensive reorganization of the cytoskeleton
12 have been identified
What does the binding of cyclin A do to the cdk2 kinase?
Without binding cyclinA, cdk2 has its substrate binding site in misalignment. With the process of cyclin A, the complex is formed causing the substrate binding site of cdk2 to become properly aligned for activity
What is the maturation factor composed of?
It is formed by cyclin B binding to cdk2
What cellular components does MPF modify?
MPF phosphorylates:
A) proteins to initiate mitosis
B) laminins in the nuclear envelope to breakdown
C) tubulin causing microtubule reorganization to form the mitosic spindle
D) histone h1 to cause condensation of chromatin
E) proteolytic enzymes that causes cleavage of cyclin B
How is the MPF activated and deactivated?
It is activated and deactivated by phosphorylation
Which are the two major suppressor genes that have an effect upon cell division cycle?
Retinoblastoma and p53
Name 3 types of bone cells
Osteoblasts
Osteoclasts
Osteocytes - osteoblasts that have become surrounded by hydroxyapatite and lose their ability to synthesize collagen
Which of these add calcium to bones, and which degrade bone, removing calcium?
Osteoblasts build up bones by adding calcium minerals
Osteoclasts degrade bone, removing calcium
What is the mechanism by which bone is cut by these cells?
Osteoclasts secrete collagenase, other enzyme and acids to tunnel through mineralized bone, forming cavities that are invaded by other cells
Name 3 major hormones involve in calcium homeostasis
Parathyroid hormone (PTH)
Calcitriol
Calcitonin
Which of the above hormones are peptides?
PTH
Calcitonin
Where is each of the above hormones synthesized?
PTH: synthesized in chief cells of the parathyroid gland
Calcitriol: synthesis starts in the skin (vitamin D precursor) then occurs in the liver, and is modified in the kidney
Calcitonin: thyroid gland
What is the effect of each of these hormones upon circulating calcium ion concentrations?
PTH: Increases the absorption of calcium from the glomerular filtrate in the kidney ie reducing renal clearance of Ca while decreasing phosphate to avoid calcification. Stimulate production of calcitriol. Increases osteoclasts activity.
Calcitriol: Responsible for translocation of calcium across the intestinal membrane against the concentration gradient (increases circulating concentration)
Calcitonin: decreases the activity and number of osteoclasts, inhibiting release of calcium from bones (decreases circulating calcium)
Where is VASOPRESSIN synthesized, secreted, and what is its function?
Synthesized in hypothalamus
Secreted by posterior pituitary (neurohypophysis)
Function: Antidiuretic
Where is OXYTOCIN synthesized, secreted, and what is its function?
Synthesized in hypothalamus
Secreted from posterior pituitary
Function: important for reproduction and lactation
Where is GROWTH HORMONE synthesized, secreted, and what is its function?
Synthesized and secreted from anterior pituitary gland (adenohypophysis)
Function: affects all metabolic processes of the body
Where is PROLACTIN synthesized, secreted, and what is its function?
Synthesized and secreted from the anterior pituitary gland (adenohypophysis)
Function: Stimulates lactation
Briefly compare the structures of vasopressin and oxytocin.
Vasopressin and oxytocin are both nonapeptides that differ only by 2 amino acids
What is the situation with respect to growth hormone and its receptors in Laron dwarfs, G.H. deficient dwarfs, pigmies, acromegaly, and gigantism?
Laron dwarfs: have excessive amounts of growth hormones, but lack hepatic receptors
GH deficient dwarfs: infant does not grow properly due to deficiency of growth hormones
Pigmies: post-GH receptor defect, normal levels of GH, low levels of IGF
Acromegaly: excessive GH secretion after epiphyseal plate closure
Gigantism: excessive GH secretion before epiphyseal plate closure, characterized by accelerated growth of long bones
Name 3 glycoprotein hormones synthesized and secreted at the anterior pituitary, and give their functions.
Thyroid stimulating hormone (TSH): stimulates thyroid gland
Follicle stimulating hormone (FSH): stimulates growth and development of ovarian follicle or spermatogenesis
Leutenizing hormone (LH): stimulates maturation of ovarian follicle, induces ovulation. Or, stimulates androgen production in males
What is the POMC family of hormones?
POMC is pro-opiomelanocortin, a family of peptides that act as hormones, neuromodulators, or neurotransmitters.
Give 3 members of POMC
Adrenalcorticotrophic hormone (ACTH): Regulates growth and function of adrenal cortex
Beta-lipotrophin hormone (Beta-LPH): causes lipolysis and fatty acid metabolism
Gamma-melanocytes stimulating hormone (gamma-MSH): causes dispersion of intracellular melanin granules resulting in skin darkening
What is Cushing syndromes?
Cushing’s syndrome is excessive production of ACTH by pituitary or by a tumor. It can produce hyperpigmentation, sodium retention (HTN and edema), glucose intolerance (diabetes), decreased eosinophils or lymphosites, increased leukocytes, etc resulting in muscle atrophy and peculiar fat distribution
What are endorphins, where are they synthesized and secreted?
Endorphins are a family of compounds that bind to the same CNS receptors as morphine and thus play a role in pain perception
Give 4 releasing hormones and 2 inhibitory factors secreted by the hypothalamus and list their functions.l
Releasing hormones:
TRH (thyrotropin releasing hormone): stimulates release of thyrotropin and prolactin
GnRH (Gonadotropin releasing hormone): stimulates the release of LH and FSH
CRH (Corticotropin releasing hormone): stimulates the release of ACTH and Beta-endorphin
GnRH (growth hormone releasing hormone)
Inhibitory factors:
GHR inhibitory factor (somatostatin): inhibits growth hormone, insulin, glucagon, gastric
PRL inhibitor: dopamine is in high concentrations in the median eminence and it does inhibition prolactin release
