mjl1717
Forum Hero
Topics: 955
Posts: 5,451
|
Those who have Cystic Fibrosis lack which ion exchange?
a)Cl and Na
b)Cl and K
c)K and Na
d)HCO3 and Cl
e)Cl and PO4
___________________
Smell the coffee! "Is That an Osler move??"
|
| doc179
Forum Guru
Topics: 67
Posts: 1,217
|
A?
|
| ralux
Forum Senior
Topics: 5
Posts: 59
|
i would go for A too..it def lacks Cl and Cl "travels" with Na...
|
| general malaise
Forum Guru
Topics: 14
Posts: 433
|
A
___________________
"El respeto al derecho ajeno es la paz" Benito Juarez
|
| mjl1717
Forum Hero
Topics: 955
Posts: 5,451
|
incorrect
___________________
Smell the coffee! "Is That an Osler move??"
|
| doc179
Forum Guru
Topics: 67
Posts: 1,217
|
is it D ?
|
| babli
Forum Guru
Topics: 40
Posts: 425
|
Aberrant HCO3- transport is a hallmark of cystic fibrosis (CF) and is associated with aberrant Cl--dependent HCO3- transport by the cystic fibrosis transmembrane conductance regulator (CFTR).
|
| general malaise
Forum Guru
Topics: 14
Posts: 433
|
D?
___________________
"El respeto al derecho ajeno es la paz" Benito Juarez
|
| mjl1717
Forum Hero
Topics: 955
Posts: 5,451
|
answer d is correct and babli described it like a pro. [I think they also mention delta 508, and most commonly a small deletion, although MANY different kinds mutaions can cause this disease.
___________________
Smell the coffee! "Is That an Osler move??"
|
| tolito
Forum Fanatic
Topics: 119
Posts: 2,164
|
babli, may i have your reference please. D appears to be the most APPROPRIATE answer but the cl/hco3 exchange does not occur in all the glands affected by cf. i know that occurs in the pancreas but i am not sure about the small intestines. in the sweat glands, the cl movement is linked with na. the negative charge created by cl in the cell drives in na. this is absent in cf so they lose na and cl in the sweat. while in the lungs, there is decrease cl secretions into mucus so na and water are reabsorbed into the cell making the mucus thick. yes the cl channel is different from the na and it is not an exchange going on but one following the other while cl is being exchanged for hco3.
i beg to differ that the fundamental problem is with the cl/hco3 exchange. to my knowledge the fundamental problem is basically with the CFTR and the ionic effect will depend on the gland. i will be glad to check out your references.
mine are big robbins p490
kaplan path
http://www-psych.stanford.edu/~wine/organs.html
and a few more i checked.
___________________
It has been a looooong hard journey but I am inches away from my destination...
|
| babli
Forum Guru
Topics: 40
Posts: 425
|
hi tolito,it's from pubmed.gov.
Cystic fibrosis (CF) is a disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR). Initially, Cl- conductance in the sweat duct was discovered to be impaired in CF, a finding that has been extended to all CFTR-expressing cells. Subsequent cloning of the gene showed that CFTR functions as a cyclic-AMP-regulated Cl- channel; and some CF-causing mutations inhibit CFTR Cl- channel activity. The identification of additional CF-causing mutants with normal Cl- channel activity indicates, however, that other CFTR-dependent processes contribute to the disease. Indeed, CFTR regulates other transporters, including Cl(-)-coupled HCO3- transport. Alkaline fluids are secreted by normal tissues, whereas acidic fluids are secreted by mutant CFTR-expressing tissues, indicating the importance of this activity. HCO3- and pH affect mucin viscosity and bacterial binding. We have examined Cl(-)-coupled HCO3- transport by CFTR mutants that retain substantial or normal Cl- channel activity. Here we show that mutants reported to be associated with CF with pancreatic insufficiency do not support HCO3- transport, and those associated with pancreatic sufficiency show reduced HCO3- transport. Our findings demonstrate the importance of HCO3- transport in the function of secretory epithelia and in CF.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd...
|
| babli
Forum Guru
Topics: 40
Posts: 425
|
A central function of cystic fibrosis transmembrane conductance regulator (CFTR)-expressing tissues is the secretion of fluid containing 100-140 mM HCO3-. High levels of HCO3- maintain secreted proteins such as mucins (all tissues) and digestive enzymes (pancreas) in a soluble and/or inactive state. HCO3- secretion is impaired in CF in all CFTR-expressing, HCO3--secreting tissues examined. The mechanism responsible for this critical problem in CF is unknown. Since a major component of HCO3- secretion in CFTR-expressing cells is mediated by the action of a Cl-/HCO3- exchanger (AE), in the present work we examined the regulation of AE activity by CFTR. In NIH 3T3 cells stably transfected with wild type CFTR and in HEK 293 cells expressing WT and several mutant CFTR, activation of CFTR by cAMP stimulated AE activity. Pharmacological and mutagenesis studies indicated that expression of CFTR in the plasma membrane, but not the Cl- conductive function of CFTR was required for activation of AE. Furthermore, mutations in NBD2 altered regulation of AE activity by CFTR independent of their effect on Cl- channel activity. At very high expression levels CFTR modified the sensitivity of AE to 4,4'-diisothiocyanatostilbene-2,2'-disulfonate. The novel finding of regulation of Cl-/HCO3- exchange by CFTR reported here may have important physiological implications and explain, at least in part, the impaired HCO3- secretion in CF.
http://www.jbc.org/cgi/content/abstract/274/6/341...
|
| tolito
Forum Fanatic
Topics: 119
Posts: 2,164
|
thanks. i read the second article and i will read the first. in the second, there is an important clarification: Except for the sweat gland , all CFTR-expressing cells of various ductal systems absorb Cl and secrete HCO3
very interesting articles.
___________________
It has been a looooong hard journey but I am inches away from my destination...
|
|
| |
| | | | | | | | | | | | | |
