jean robert
Forum Guru
Topics: 144
Posts: 596
|
B
___________________
Great works are performed not by strength, but by perseverance.
|
| pr20
Forum Senior
Topics: 18
Posts: 162
|
I will go with B.
Leukemia in a man from japan,retroviral DNA---->these point towards HTLV-1 which is a retrovirus like HIV.
I was confused between B and E choices....but recent infection cannot cause acute leukemia...it takes many years of infection with HTLV-1 to develop leukemia....so I will go with B because HTLV-1 is an pro-oncogenic virus.
|
| new_n_lost
Politically InCorrect
Topics: 644
Posts: 5,910
|
B. Oncogene from HTLV-1 may have triggered the development of leukemia
___________________
FORUM RULES-- Those who believe in telekinesis, raise my hand. I get enough exercise just by pushing my luck --P4U World.." The pure and simple truth is rarely pure and never simple."
|
| silver
Forum Guru
Topics: 21
Posts: 754
|
B
___________________
Everything turns out ok in the end. If it's not ok, then it's not the end. Expect the worst, and hope for the best.
|
| Tiff
Forum Guru
Topics: 49
Posts: 500
|
|
| new_n_lost
Politically InCorrect
Topics: 644
Posts: 5,910
|
A. Environmental factors in Japan may have promoted the development of type 1 human T-cell lymphotropic virus (HTLV-1) leukemia
Cos A didnt make sense to me in the first place unless we include breast feeding and blood transfusion as envoirnmental factors ( i guess we do include it if i m right ) and Choice D again has nothing to do with it. so i m stumped with this one. One very interesting thing i learned is that HTLV is not an endogenous virus and also its not a pro-oncogenic virus. And the presence of HTLV - 2 leads to increased conversion from HIC to AIDS but the other way around is yet to be found.
I hope i m right
___________________
FORUM RULES-- Those who believe in telekinesis, raise my hand. I get enough exercise just by pushing my luck --P4U World.." The pure and simple truth is rarely pure and never simple."
|
| Tiff
Forum Guru
Topics: 49
Posts: 500
|
The correct answer is C (presence of retroviral DNA may be due to endogenous virus). The stem of the question does not define the retroviral sequences that were amplified by PCR. Because PCR is such a highly sensitive technique, endogenous retroviruses can be amplified when it is used. Although HTLV-1 is endemic in southern Japan, the presence of retroviral DNA is not proof that HTLV-1 is involved in the disease.
|
| silver
Forum Guru
Topics: 21
Posts: 754
|
it looks like a duck, sounds like a duck, walks like a duck.....BUT we're not going to call it a duck!!!
___________________
Everything turns out ok in the end. If it's not ok, then it's not the end. Expect the worst, and hope for the best.
|
| silver
Forum Guru
Topics: 21
Posts: 754
|
Tiff wrote: the presence of retroviral DNA is not proof that HTLV-1 is involved in the disease.
It's an established fact that there is a co-relation between leukemia and HTLV-1.....which is why he's being tested. the results indicate presence of a retroviral DNA. which other retrovirus is there that you're trying to coorelate with leukemia??? obviously it's going to be HTLV-1!!!!
that's like coming across a pool of mud, with muddy shoes and muddy footprints but then saying that the mud on the shoes is NOT from this mud.
___________________
Everything turns out ok in the end. If it's not ok, then it's not the end. Expect the worst, and hope for the best.
|
| Tiff
Forum Guru
Topics: 49
Posts: 500
|
I admit it's a little shady. But I guess this is what the exam is all about. Not just recognizing the right answer, but the best answer and eliminating the distractors. 
|
| Tiff
Forum Guru
Topics: 49
Posts: 500
|
Here is the explanation for the incorrect answer A:
Environmental factors have not been identified for induction of HTLV-1 leukemia
|
| silver
Forum Guru
Topics: 21
Posts: 754
|
Tiff wrote:I admit it's a little shady. But I guess this is what the exam is all about. Not just recognizing the right answer, but the best answer and eliminating the distractors.
well, it's also important to study from accurate and authentic sources/books/study materials. the sources i've used (eMedicine, New England Journal of Medicine, etc) to look up this question say something entirely different and base their explanations on scientific facts.
perhaps your source for this ques. is legit., but from everything i've read it just isn't adding up.
anyways, interesting......
___________________
Everything turns out ok in the end. If it's not ok, then it's not the end. Expect the worst, and hope for the best.
|
| Tiff
Forum Guru
Topics: 49
Posts: 500
|
Silver - do you have materials that indicate that environmental factors actually induce HTLV? Something that is associated doesn't actually mean that it causes it. I would like to see any information please to disprove this possibly difficult question. Please post the explanations and scientific fact that disprove the validity of this question. I'm sure we all can learn from it. Thank you.
|
| Tiff
Forum Guru
Topics: 49
Posts: 500
|
By the way, learning and improving our knowledge is something we all will be obliged to do throughout our careers. I would hope that we all are attempting to use accurate and authentic resources. 
|
| new_n_lost
Politically InCorrect
Topics: 644
Posts: 5,910
|
Tiff wrote:
The correct answer is C (presence of retroviral DNA may be due to endogenous virus). The stem of the question does not define the retroviral sequences that were amplified by PCR. Because PCR is such a highly sensitive technique, endogenous retroviruses can be amplified when it is used. Although HTLV-1 is endemic in southern Japan, the presence of retroviral DNA is not proof that HTLV-1 is involved in the disease.
Are you absolutely sure that presence of retroviral DNA is not proof that HTLV -1 is not involved.
Can you provide the resource where you have read that presence of HTLV1 is not significant in T-Cell leukemia.
Where is this question from cos i have Levinsion's Microbiology Board Review 8thed pg 304 which says that :-
"HTLV-1 is not an endogenous virus; ie, proviral DNA corresponding to its RNA genome is not found in normal human cell DNA. It is an exogenously acquired virus, because its proviral DNA is found only in the DNA of the malignant lymphoma cells. It infects CD4-positive T cells preferentially and will induce malignant transformation in these cells in vitro.
After infection of the cell by a retrovirus, the following events occur. Using the genome RNA as the template, the reverse transcriptase (RNA-dependent DNA polymerase) synthesizes double-stranded proviral DNA. The DNA then integrates into cellular DNA. Integration of the proviral DNA is an obligatory step, but there is no specific site of integration. Insertion of the viral LTR can enhance the transcription of adjacent host cell genes. If this host gene is a cellular oncogene, malignant transformation may result. This explains how retroviruses without viral oncogenes can cause transformation. "
And from Lippincott Microbiology 2001 ed pg 376
" B. Pathogenesis and clinical significance of adult T-cell leukemia
HTLV-1 infection both stimulates mitosis and immortalizes T-lymphocytes, which acquire an "antigen-activated" phenotype. Following infection, the virus becomes integrated in the host cell as a provirus, and transforms a polyclonal population of T cells. Although these cells all have an integrated provirus, there is no common integration site in different tumors. No HTLV mRNA is transcribed, and no recognized oncogene is activated. However, in the course of continued multiplication over a period of many years, the infected T-cells accumulate many chromosomal aberrations, leading to selection of monoclonal populations of cells that have an increasingly malignant phenotype (Figure 31.20). "
Both sources say that HTLV is not an endogenous virus.
Moreover can please explain this part to me." The stem of the question does not define the retroviral sequences that were amplified by PCR." like though it doesnt say that its HTLV but is there any other RETROVIRUS which causes T-CELL Leukemia. Yes the stem of the question hasnt provided or named the Acute Leukemia as Adult T-Cell.
And also this assumption that HTLV-1 doesnt cause or is not necessary for the progression of Adult T-Cell Leukemia is absolutely wrong.
" In Japan the zones of endemic HTLV-I are distributed heterogeneously, except for clusters in the Kyushu and Okinawa prefectures, where more than 30 percent of the population is seropositive in some districts. Although HTLV-I infection is necessary for the development of disease, adult T-cell leukemia or HTLV-I myelopathy develops in only a small proportion of infected subjects. Overall, some 98 percent of those with HTLV-I infection are likely to remain asymptomatic carriers. Approximately 1 percent of the Japanese population are HTLV-I carriers but the lifetime risk of adult T-cell leukemia in a carrier is estimated to be 2 to 4 percent; the risk is similar in Jamaica." Ref NEJM.
Yes the argument can be made that in Southern Japan not everyone will have T-cell Leukemia. But every T-Cell leukemia patient in Southern Japan will have HTLV 1 virus infection. that has been proved and acknowledged.
As the choice says that the presence of Retroviral DNA in a leukemic patient maybe due to an endogenous virus seems to be wrong. like retrovirus present in a T-cell of patient with leukemia who is coming from an area where a particular retrovirus is in endemic proportions is not the exact retrovirus which is prevalent is a bit off the mark. Endogenous virus are ones which are incorporated in the DNA and would there fore make all Tcells like this.
And please do tell us the source if you wish because there are mistakes in Qbanks as well.
___________________
FORUM RULES-- Those who believe in telekinesis, raise my hand. I get enough exercise just by pushing my luck --P4U World.." The pure and simple truth is rarely pure and never simple."
|
| Tiff
Forum Guru
Topics: 49
Posts: 500
|
Endogenous retroviruses are a kind of retrovirus that are believed to have been acquired from ancient infections of the human germ cells, as well as the germ cells of mammals and other vertebrates. Because of this, their proviruses are passed down or inherited by the next generation and because of this it now resides in the genome. Retroviruses are viruses that can actually copy their RNA into DNA and then proceeds to integrate it into the genome of the host. In general, most retroviruses infect somatic cells, but there are also cases when some retroviruses can also infect germline cells. When this happens then the RNA integrated DNA genome is inherited by the next generation. Thus it is known as endogenous.
Endogenous viruses, because of the way they have been integrated into the genome can actually persist for a very long period of time – in fact, it can remain for tens of millions of years. The good thing though is that it only gets infectious for a short period time, usually after integration, since they get mutations that would have a “knockout” effect at the point where the host DNA is replicated. It is also possible for endogenous retrovirus to be excised (even though just in part) from the genome. This is done through a process called recombinational deletion. http://www.iscid.org/encyclopedia/Endogenous_Retr...
In this question it mentions that PCR picked up presence of retroviral DNA. Because PCR it's so sensitive it can pick of endogenous retroviruses. The answer choice is not referring to HTLV. It simply is referring to endogenous retroviruses. Because the guy is from Japan, and has leukemia, HTLV became a distractor.
The question is from rapid review micro. Hope this helped.
|
| new_n_lost
Politically InCorrect
Topics: 644
Posts: 5,910
|
@ Tiff
The chances of having a endogenous virus in a patient who is coming from Southern Japan with acute leukemia instead of HTLV-1 is sort of same as the chances of a person coming from Africa with a opportunistic infection with a retrovirus on PCR is actually not HIV but a virus incorporated in the genome some thousands of years earlier. The statement kinda defeats the logic ( to me atleast).
I agree with the efforts on part of the authors to give introduction to the concept of Endogenous Retrovirus or Human Endogenous Retrovirus Virus (HERV) but i mean cmon do you actually know that 8% of the human genome is built on retroviral material and yet the ERVs become non infectious. And they are mostly just sitting and their function or role in disease is still theoritical rather than factual. And the chances of them coming up on a PCR are relatively few. http://genomebiology.com/2001/2/6/reviews/1017. I think that the authors were trying to elicit the point that HERVs have shown up in PCRs of MS patients but they werent in no way or form involved with the disease.
I believe that question was poorly written but its only my opinion and based on my interpretation of articles i have read.
___________________
FORUM RULES-- Those who believe in telekinesis, raise my hand. I get enough exercise just by pushing my luck --P4U World.." The pure and simple truth is rarely pure and never simple."
|
| Tiff
Forum Guru
Topics: 49
Posts: 500
|
NNL - I see your perspective and I think you make an excellent argument. I still have to ask myself how should one derive the best answer in this circumstance. What makes sense to me is...that one of the purposes of this question is to acknowledge that environmental factors may be associated and related but to understand that because it is endemic to the area probably doesn't mean that environmental factors actually cause it making another answer the best option. Perhaps I'm reading too much into this but when I get something wrong, I really want to understand why. Or maybe you're just right and the question was poorly written which is also possible.
|
| oldkidontheblock
Forum Guru
Topics: 40
Posts: 826
|
new_n_lost wrote:
I believe that question was poorly written but its only my opinion and based on my interpretation of articles i have read.
have to agree here with NNL the question seems to be very poorly written.
___________________
Malcolm Forbes: Victory is sweetest when you've known defeat
|
| Tiff
Forum Guru
Topics: 49
Posts: 500
|
Hopefully the exam questions won't be like this. 
|
| icarus
Forum Senior
Topics: 27
Posts: 149
|
it looks like a duck, sounds like a duck, walks like a duck.....BUT we're not going to call it a duck!!!
Great One Buddy looool laughed my heart out
Kind regards
IcarusMD
___________________
The Maestro says its Mozart...but it sounds like bubble gum
|
|
| |
| | | | | | | | | | | | | | | | | | | | | |
