Biomedical Engineering Reference
In-Depth Information
2-year bioassay. There are not much published data on historical tumor
rates in rats over 2 years of age. Ramazzini Foundation has 20 years of
data on about 2000 control males and females that were allowed to live
until spontaneous death. This would be useful to gets time to historical
tumor data especially after 2 years. An increase in leukemia/lymphoma
was reported by Ramazzini Foundation using the lifetime study design
in at least seven chemicals, but not in the other studies in the literature of
the same chemicals, which used a standard 2-year design (Clary, 2007).
In one of the chemicals (MTBE), the top dose males lived significantly
longer than the control males but had a lower incidence of leuke-
mia/lymphoma than the control (Belopoggi et al., 1997). Background
tumor data in animals more than 2 years old is limited. Increase in
normal old age tumors can also be a confounding factor.
In a review of the Ramazzini Foundation aspartame study by EFSA
(2006), chronic respiratory disease and poor survival was reported; in
their evaluation survival ranged from 22% to 45% at 103 weeks. EFSA
concluded that the increased incidence of lymphomas/leukemias
reported in treated rats was unrelated to aspartame, given the high
background incidence of chronic inflammatory changes in the lungs
and the lack of a positive dose-response relationship. It is possible that
questionable diagnosis of some tumors can arise as a result of abundant
lymphoid hyperplasia in the lungs of rats suffering from chronic
respiratory disease.
A review of the possible role of Mycoplasma pulmonis and diagnosis
of lymphomas in the Ramazzini Foundation aspartame, MTBE and
methanol studies were conducted (Schoeb et al., 2009). In all three
studies, the most commonly reported hematopoietic tumor was lym-
phoimmunoblastic lymphomas. It was found in high percentages in the
lung and as many as 50% of the time lymphoimmunoblastic lymphomas
were reported only in the lung and not at other site. In the Ramazzini
Foundation methanol study, the incidence of lymphoimmunoblastic
lymphomas reported only in the lung ranging from 33.3% to 56.3% for
all groups Lymphoimmunoblastic lymphomas are normal a rare tumor
in Sprague Dawley rats. In the lung, neurtrophils, plasma cell, and
lymphocytes accumulation are typically seen following an infection of
M. pulmonis rather than a rare form of lymphomas. Schoeb et al. (2009)
Search WWH ::




Custom Search