The biological fate of the fish feed additive, ethoxyquin (EQ) was examined in the muscle of Atlantic salmon during 12 weeks of feeding followed by a 2 weeks depuration period. Parent EQ (1,2-dihydro-6-ethoxy-2,2,4-trimethylquinoline), quinone imine (2,6-dihydro-2,2,4-trimethyl-6-quinolone), de-ethylated EQ (6-hydroxy-2,2,4-trimethyl-1,2-dihydroquinoline) and EQDM (EQ dimer or 1,8'-di(1,2-dihydro-6-ethoxy-2,2,4-trimethyl-quinoline) were found to be the ubiquitous metabolites of dietary EQ, with EQDM as a main metabolite. A rapid decrease in the level of EQ (2.4 days of half-life) was balanced by an increase in EQDM, giving an unchanged net sum following 2 weeks of depuration. The mandatory 14 days depuration period prior to slaughtering of farmed salmon in Norway was not sufficient for complete elimination of EQ-derived residuals. Post depuration, EQDM accounted for 99% of sum of the two compounds in all treatment groups; possible toxicological effects of EQDM are not known. The individual concentrations of EQ and EQDM and their sum are dependent on EQ level in the feed, consequently, their residual concentrations may be controlled. The theoretical amount of EQ and EQDM consumed in one meal of farmed salmon would be under the recommended ADI, provided that the fish were raised on feed with no more than 150 mg EQ/kg feed, which is the EU maximum limit for EQ in fish feed.
Fiber type shifts in aging skeletal muscle have been studied with myofibrillar ATPase histochemistry and gel electrophoresis, but less commonly with immunohistochemistry. Immunohistochemical study of myosin heavy chains (MHCs) in single myofibers yields additional information about aged skeletal muscle. Furthermore, many studies of aging rodent skeletal muscle have been performed on fast-MHC-predominant muscle and in several different strains. The aim of this study was to evaluate immunohistochemically MHC characteristics in the slow-MHC-predominant soleus muscle in the Fischer Brown Norway F1 hybrid aging rat (FBN). Three age groups of FBN rats were studied: 12 months, 30 months, and 36 months. Soleus muscles were excised, quick-frozen, and stained immunohistochemically for slow, fast, developmental, and neonatal MHC isoforms. Cross-sections were evaluated for the number and cross-sectional areas of fibers expressing each isoform. Single myofibers in soleus muscles of the aged rats showed significantly greater amounts of coexpression of slow and fast MHC than did younger animals. This change began by 30 months of age, but did not reach statistical significance until 36 months of age. The soleus from 36-month-old rats also expressed greater amounts of developmental MHC than did the other groups. These developmental MHC-positive myofibers also coexpressed either slow or slow and fast MHC. The age-related increase in MHC coexpression of slow with fast isoforms may indicate a fiber type shift suggestive of denervation that outpaces reinnervation. The developmental MHC-positive fibers provide evidence of ongoing myofiber remodeling in the oldest rats in the midst of the fiber degeneration of aging.
Aging of skeletal muscle is often accompanied by muscle atrophy and it appears that apoptosis plays an important role in this process. The detailed mechanism(s) is not completely understood, however. In this study, we examined expression of the apoptosis regulatory proteins as well as the heat shock proteins, which have been shown to modulate the apoptotic process in certain cell types, in order to more completely elucidate apoptotic signaling in aged skeletal muscle. To more specifically identify alterations that are likely to be the result of aging, we compared 16-month-old middle-aged (MD) and 29-month-old senescent (SE) male Fischer 344 x Brown Norway rats in our study. Our results show that the degree of DNA laddering was higher in SE compared to MD rats. Using total tissue homogenates we examined the level of expression of several apoptosis-related proteins in two categories: mitochondria-associated proteins and caspases. Of the mitochondria-associated proteins, the levels of p53 showed a significant increase in SE compared to MD rats. There was also a significant increase in the expression of Bax, Bcl-2 and Apaf-1 in SE rats over that of MD rats; cytochrome c and AIF levels remained unchanged, however. Regarding the caspases, there were increases in the levels of pro-caspases-12 and -7 and cleaved caspase-9, although the levels of pro- and cleaved caspase-3 as well as cleaved caspase-12 remained unchanged. Furthermore, our results showed significant increases in HSP27, HSP60, and the inducible HSP70. These data show that in rat skeletal muscle increased apoptosis occurs between middle-age and senescence, indicating an aging-related increase in apoptosis in skeletal muscle. The involvement of different apoptotic pathways in the aging process is suggested by the selective alterations in the apoptosis regulatory proteins. The increased expression of the HSPs suggests a relationship between HSPs and the aging-related apoptotic process.
Waterborne radioactive releases into the Techa River from the Mayak Production Association in Russia during 1949-1956 resulted in significant doses to about 30,000 persons who lived in downstream settlements. The residents were exposed to internal and external radiation. Two methods for reconstruction of the external dose are considered in this paper, electron paramagnetic resonance (EPR) measurements of teeth, and fluorescence in situ hybridization (FISH) measurements of chromosome translocations in circulating lymphocytes. The main issue in the application of the EPR and FISH methods for reconstruction of the external dose for the Techa Riverside residents was strontium radioisotopes incorporated in teeth and bones that act as a source of confounding local exposures. In order to estimate and subtract doses from incorporated (89,90)Sr, the EPR and FISH assays were supported by measurements of (90)Sr-body burdens and estimates of (90)Sr concentrations in dental tissues by the luminescence method. The resulting dose estimates derived from EPR to FISH measurements for residents of the upper Techa River were found to be consistent: The mean values vary from 510 to 550 mGy for the villages located close to the site of radioactive release to 130-160 mGy for the more distant villages. The upper bound of individual estimates for both methods is equal to 2.2-2.3 Gy. The EPR- and FISH-based dose estimates were compared with the doses calculated for the donors using the most recent Techa River Dosimetry System (TRDS). The TRDS external dose assessments are based on the data on contamination of the Techa River floodplain, simulation of air kerma above the contaminated soil, age-dependent lifestyles and individual residence histories. For correct comparison, TRDS-based doses were calculated from two sources: external exposure from the contaminated environment and internal exposure from (137)Cs incorporated in donors' soft tissues. It is shown here that the TRDS-based absorbed doses in tooth enamel and muscle are in agreement with EPR- and FISH-based estimates within uncertainty bounds. Basically, this agreement between the estimates has confirmed the validity of external doses calculated with the TRDS.
The Norwegian spring spawning (NSS) herring is an ecologically and economically important fish population in the Norwegian Sea. It was the first of several Norwegian fish stocks subject to a baseline study designed to give a comprehensive account of the levels of contaminants in a fish species from most of its area of distribution and during different seasons. During 2006 and 2007, 800 individual herring were sampled in their feeding areas in the Norwegian Sea in spring and autumn and at their spawning grounds off the coast of Norway during late winter. Metals including Hg, Cd, As and Pb were determined in muscle samples of individual herring, and mean concentrations±sd (mg kg(-1) ww) were: Hg: 0.04±0.03, Cd: 0.010±0.006, As: 2.2±0.6 and Pb:
Limb girdle muscular dystrophy (LGMD) type 2A is caused by mutations in the CAPN3 gene and complete lack of functional calpain 3 leads to the most severe muscle wasting. Calpain 3 is suggested to be involved in maturation of contractile elements after muscle degeneration. The aim of this study was to investigate how mutations in the four functional domains of calpain 3 affect muscle regeneration.
We studied muscle regeneration in 22 patients with LGMD2A with calpain 3 deficiency, in five patients with LGMD2I, with a secondary reduction in calpain 3, and in five patients with Becker muscular dystrophy (BMD) with normal calpain 3 levels. Regeneration was assessed by using the developmental markers neonatal myosin heavy chain (nMHC), vimentin, MyoD and myogenin and counting internally nucleated fibers.
We found that the recent regeneration as determined by the number of nMHC/vimentin-positive fibers was greatly diminished in severely affected LGMD2A patients compared to similarly affected patients with LGMD2I and BMD. Whorled fibers, a sign of aberrant regeneration, was highly elevated in patients with a complete lack of calpain 3 compared to patients with residual calpain 3. Regeneration is not affected by location of the mutation in the CAPN3 gene.
Our findings suggest that calpain 3 is needed for the regenerative process probably during sarcomere remodeling as the complete lack of functional calpain 3 leads to the most severe phenotypes.
Notes
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Effects of chemical contaminant exposure may be contributing to the decline of spectacled eiders (Somateria fischeri) nesting in coastal areas of western Alaska. We evaluated chemical exposure and potential effects in 20 male eiders collected near St. Lawrence Island, Alaska. Analytes included metals, trace elements, chlorinated organics, and (137)Cesium ((137)Cs). Effects of contaminant exposure were evaluated using histopathology and biochemical measures of porphyrin profiles, cytochrome P450 activities, and metallothionein (MT) concentrations. Copper, cadmium, and selenium concentrations were elevated in spectacled eiders when compared to literature values for other marine birds. Only a few samples had trace concentrations of chlorinated organic compounds. Muscle (137)Cs levels were all below the average minimum quantifiable concentration of 0.079 Bq/g. No histopathological lesions were associated with elevated contaminant concentrations in liver, kidney, or testes. Protoporphyrin was found in highest concentration in both the liver and kidneys, followed by coproporphyrin and uroporphyrin, respectively. Hepatic uroporphyrin concentrations correlated significantly to hepatic arsenic concentrations. Mean activities of hepatic EROD, MROD, BROD, and PROD were consistent with other avian species. Comparisons of cadmium/MT ratios from this study to published literature ratios in seven marine avian species suggest that, although adult male spectacled eiders have elevated liver concentrations of certain MT-inducing metals, their MT concentrations are not as strongly induced as would be predicted based on literature values. Despite elevated metal concentrations, the apparent good health of the St. Lawrence Island birds suggests that should these contaminants be a factor in population declines, they likely act by decreasing fecundity or survival of young rather than via direct health impacts on adult male spectacled eiders.
DDT isomers were detected in all the liver and muscle samples of Greenland sharks Somniosus microcephalus (n?=?15) caught in Greenland seawaters. The mean concentrations of SDDTs (sum of o,p' and p,p' DDT, DDD, and DDE isomers) were 1094?±?818 ng/g lipid weight (lw) in the muscle and 761?±?416 ng/g lw in the liver. The p,p'-DDE accounted for 48%?±?41% and 53%?±?54% of the total DDT residue in the white muscle and liver, respectively. The lipid content was 48%?±?10% in the muscle and 43%?±?17% in the liver. Female sharks showed the highest concentrations of SDDTs. The youngest shark showed higher concentrations of SDDTs in the liver than the older sharks. To our knowledge, this is one of the few investigations on DDT levels in S. microcephalus where concentrations were correlated to lipid content and sex/size.
OBJECTIVES: To evaluate the influence of established liver cirrhosis on muscle strength and muscle contents of magnesium (Mg), potassium (K) and sodium, potassium pumps (Na,K-pumps) in chronic alcoholic patients. DESIGN: An open cross-sectional study. SETTING AND SUBJECTS: Forty consecutive chronic alcoholics (18 with cirrhosis and 22 without cirrhosis) admitted to the Department of Hepatology, Aarhus University Hospital, Denmark, or to a collaborating alcoholism treatment centre, and 36 healthy control subjects. MAIN OUTCOME MEASURES: Evaluation of participant's subjective physical ability and measurement of maximum isokinetic muscle strength and muscle mass, as well as measurements of Mg, K and Na,K-pumps in skeletal muscle. RESULTS: Maximum isokinetic muscle strength and muscle mass were equally reduced in patients with and without cirrhosis (P
Department of Environment and Resource Studies, University of Waterloo, 200 University Ave. West, Waterloo, ON N2L 3G1, Canada. ljtsuji@fes.uwaterloo.ca
Recently, the use of lead isotope ratios has definitively identified lead ammunition as a source of lead exposure for First Nations people, but the isotope ratios for lead pellets and bullets were indistinguishable. Thus, lead-contaminated meat from game harvested with lead bullets may also be contributing to the lead body burden; however, few studies have determined if lead bullet fragments are present in big game carcasses. We found elevated tissue-lead concentrations (up to 5,726.0 microg/g ww) in liver (5/9) and muscle (6/7) samples of big game harvested with lead bullets and radiographic evidence of lead fragments. Thus, we would advise that the tissue surrounding the wound channel be removed and discarded, as this tissue may be contaminated by lead bullet fragments.
