I should really thank Dr. Curtis for his good comment,
but I think something should be noted here:
1- Despite the fact that background aberrations are
usually negligible, there is usually no difference between
this value and the frequency of aberrations induced by
a common adapting dose (e.g. 1cGy). Let's consider the
early report of Shadley and Wolff (1987);
Control       6 Aberr in 200 cells
1cGy          9
1.5Gy         83
1cGy+1.5 Gy   60  Expected=83+9-6=86
2- Obviously, the net freq. of aberrations induced by 1cGy is
(9-6) and the net freq. of aberrations induced by 1.5Gy is
(83-6). So the expected frequency of aberrations is
83+9-(2.6)=80
Regards, Javad Mortazavi
>If so, I think subtracting only one "control" value is correct.
>
>S.M. Javad Mortazavi wrote:
>> 
>> Dear Members;
>> 
>> Good night
>> 
>>    Usually, in adaptive response (AR) studies, the frequency of chromosome aberrations
> induced by both adapting and challenge doses is compared with the
>expected frequency of
> aberrations to determine
>> whether this difference is statistically significant or not. The determination of
> expected values sound to be very problematical. Pioneer AR researchers
>used the
> following equation:
>> Exp = the sum of the frequencies of aberrations of each dose (Adapting + Challenge) -
> Controls (non-irradiated samples).
>> Since the background aberrations are included in the frequencies of aberrations
> induced by adapting dose or challenge dose alone, it seems that we
>should change the
> above equation into:
>> Exp = the sum of the frequencies of aberrations of each dose - 2 Controls.
>> Any comment or correction will be highly appreciated.
>> 
>> Regards
>> Javad Mortazavi
>> ---
>> 
>> S. M. Javad Mortazavi, Ph.D candidate
>> Medical Physics Department
>> School of Medical Sciences
>> Tarbiat Modares University
>> P.O. Box 14115-111
>> Tehran, Iran
>> 
>> Visit our web site on Low Dose Radaition, Hormesis and Adaptive Response at URL:
>> http://www.angelfire.com/mo/radioadaptive
>> 
>> Angelfire for your free web-based e-mail. http://www.angelfire.com
>
>-- 
>
>**********************************
>
>Stanley B. Curtis, Ph.D.
>Fred Hutchinson Cancer Research Center
>1100 Fairview Avenue N.  MS-665
>P.O. Box 19024
>Seattle, WA 98109-1024
>
>Tel. (206) 667-2685
>Fax  (206) 667-7004
>[log in to unmask]
>
>**********************************
>


Angelfire for your free web-based e-mail. http://www.angelfire.com


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%