The Toxicologist - Society of Toxicology

2430 TOXICITY OF RIBBON WORM CEPHALOTHRIX
SPECIES ON THE SURFACE OF THE SHELL OF
CULTURED OYSTERS IN HIROSHIMA BAY,
HIROSHIMA PREFECTURE, JAPAN.
M. Asakawa. Graduate Schoool of Biosphere Science, Hiroshima University, Higashi-
Hiroshima, Japan.
Paralytic toxicity of a species of ribbon worms identified as a member of the genus
Cephalothrix, found on the shells of cultured oysters in Hiroshima Bay, was examined
between November and May from 1998 to 2005 by the standard bioassay
method for tetrodotoxin (TTX). The toxicity study showed that all of the 764 specimens
examined were found to contain toxins with strong paralytic action in mice
throughout the season covered. Their toxicity scores ranged from 169 to 25,590
mouse units (MU) per gram for whole body. About eighty percent of the total individuals
were ranked as ‘strongly toxic’ (1,000 MU/g). Forty-eight percent of the
total specimens possessed toxicity scores more than 2,000 MU/g. The highest toxicity
detected was 25,590 MU/g in a specimen collected on June 25, 1999. The total
toxicity of this particular specimen was roughly calculated to be 5,631 MU, the
value that is approximately equivalent to half of the minimum lethal dose of TTX
in human. Some seasonal variations of toxicity of this ribbon worm could be recognized.
Specimens collected on October 28, 2004 to January 20, 2005 showed mean
toxicities of 1,855-4,076 MU/g. But on February 22, 2005, their toxicities had
sharply decreased down to a mean of 1,578 MU/g. At the beginning of December,
their toxicities increased to a mean of 4,510 MU/g. This paralytic toxin was isolated
and recrystallized. The recrystallized toxin showed a specific toxicity of 3,520
MU/mg. This toxin was finally identified as TTX by the instrumental analysis. As
the culturing of edible bivalves such as oysters and scallops is a flourishing industry
in Japan, surveillance for the distribution of toxic ribbon worms in other areas besides
Hiroshima Bay is urgently needed.
2431 DIFFERENTIAL HEAT STABILITY OF RACTOPAMINE
IN LIQUID AND PROTEIN MATRICES.
C. Chou 1 , P. Lan 1 , M. Hsieh 2 and W. Chang 3 . 1 Veterinary Medicine, National
Chung-Hsing University, Taichung, Taiwan, 2 Graduate Institute of Microbiology and
Public Health, National Chung-Hsing University, Taichung, Taiwan and 3 Animal
Disease Diagnostic Center, National Chung-Hsing University, Taichung, Taiwan.
Ractopamine (RAC) is a β-adrenergic agonist approved to be used as a growth promoter
in livestock production in the USA, Australia and Canada. However, RAC is
banned in Europe, China and Taiwan due to its potential risks linked to adverse
cardiovascular effects and deaths caused by residues in visceral tissues. In order to
have a more accurate estimation of consumer exposure to RAC, its heat stability
was evaluated in different heating processes (water bath, microwave, autoclave),
heating lengths (100 o C: 15, 30, 60, 120 min), and matrices (water, soybean sauce,
beef, pork, and swine liver, kidney, lung). RAC degradation was determined by
high performance liquid chromatography with UV detection. Results indicated
that regardless of heating processes, RAC degradations in water were all below
13.1%, but structural degradation was accelerated in soybean sauce (35.5%). In
protein matrices, degradation also increased and ranged from 24.4-46.4%. Heat
stability was ranked as beef>beef/pork in soybean sauce>swine liver>swine kidney
>pork>swine lung, indicating differential heat stability of RAC in different protein
matrices, with significantly lower (p