Lack of In Vivo Mutagenicity of Acetamide in a 13-Week Comprehensive Toxicity Study Using F344 gpt Delta Rats

Acetamide, a food contaminant, has been shown to induce hepatocellular tumors in rats. However, the mode of action underlying acetamide-induced hepatocarcinogenesis remains unclear. In the current study, we aimed to examine the possible involvement of in vivo mutagenicity in hepatocarcinogenesis of acetamide and evaluate its toxicological profile using a comprehensive medium-term toxicity study in gpt delta rats. Six-week-old male F344 gpt delta rats were given a basal diet containing 0%, 0.625%, 1.25%, or 2.5% acetamide for 13 weeks. In general toxicologic assessment, hepatotoxic parameters in serum, such as aspartate aminotransferase and alanine aminotransferase were significantly changed at the 1.25% group and higher. Histopathological examination of the liver revealed that various changes related to hepatic injury were observed at the 1.25% group and higher. Interestingly, Feulgen-positive cytoplasmic inclusion was frequently observed in hepatocytes in these groups. In the hematopoietic system, red blood cell parameters in plasma, such as mean corpuscular volume and mean corpuscular hemoglobin were significantly changed at the 1.25% group and higher, and decrease of erythroblast in the spleen was observed histopathologically in the 2.5% group. Thus, the no-observed-adverse-effect level of acetamide in this study was 0.625% (equivalent to 394 mg/kg body weight/day). In vivo mutation assays showed that acetamide induced no changes in gpt and red/gam gene mutant frequencies, even at the carcinogenic target site. In contrast, Ki67-positive hepatocytes were increased significantly at carcinogenic doses. Therefore, these results suggested that cell proliferation activity, but not mutagenicity, played crucial roles in acetamide-induced hepatocarcinogenesis in rats.

LGMD1D myopathy with cytoplasmic and nuclear inclusions in a Saudi family due to DNAJB6 mutation

Autosomal dominant LGMD1D has been described in multiple families in Asia, Europe, and USA. However, to the best of our knowledge, no cases of LGMD1D have been reported among native Bedouin Saudi families. Fifty Saudi families with LGMD were analyzed and the causative underlying genes were studied utilizing genome wide linkage, homozygosity mapping, and neurological gene panel. We identified one family of a Bedouin origin with LGMD1D. Two patients had progressive proximal and distal weakness, dysphagia, and respiratory symptoms. Creatinine kinase was normal. Muscle biopsy showed marked variation in myofibers size with scattered angular atrophic fiber, necrotic fibers, and myophagocytosis, with red-rimmed vacuoles depicting a sarcoplasmic body. Heterozygous c.C287T (p.P96L) variant in exon 5 of DNAJB6 (NM_005494) gene was found. This change is localized within glycine and phenylalanine rich domain and alter an amino acid residue. Our findings will expand on the existing genotypic and phenotypic spectrum of this disorder and aid in elucidating hidden mechanisms implicated in LGMD1D.

[Virus-induced compartimentalization: aggresomes, cytoplasmic inclusions and viral factories]

Some viruses induce, in the infected cells, the formation of cytoplasmic inclusions that are known to contain viral proteins. These viral inclusions that share some characteristics of aggresomes have been considered as sideproducts of the infectious process without any role and resulting from the accumulation and aggregation of large quantities of proteins produced in excess during infection. However, recent results obtained on some viral families suggest that these inclusions have different functions: they can be sites of specific degradation of antiviral proteins or viral factories where essential viral steps (transcription/replication, translation, viral assembly) take place. It is supposed that the viruses-induced compartimentalization is the result of cellular defense mechanisms, which would be diverted by virus for their own replication.

Changes in the amount of cytoplasmic inclusions in mouse oocytes during meiotic maturation in vivo and in vitro

Background and aims: The changes in cytoplasmic inclusions during meiotic maturation have only been examined in porcine oocytes. In the present study, the amount and the number of cytoplasmic inclusions (glycogen granules, lipid droplets and fibrous structures) were examined in mouse oocytes in the process of in vivo and in vitro maturation. For those inclusions that changed in amount during maturation, we also examined their content in oocytes treated with olomoucine, an inhibitor of cyclin-dependent kinase, in order to clarify the relationship between nuclear maturation and changes in the inclusions. Methods: Nuclear maturation in the oocytes cultured for various periods and those collected from antral follicles and oviducts was examined after staining with aceto-orcein. For the demonstration of glycogen granules and lipid droplets, oocytes were stained with periodic acid-Schiff or Sudan IV. Fibrous structures in the oocytes were observed under an electron microscope. Results: The amount of glycogen granules, Sudanophilic lipid droplets and fibrous structures did not change in the oocytes matured in vivo and in vitro, whereas the number of the lipid droplets increased during maturation. In the oocytes treated with olomoucine, the resumption of nuclear maturation was inhibited, whereas the increase in the number of Sudanophilic lipid droplets was not inhibited. Conclusion: Present findings suggest that the increase in the number of Sudanophilic lipid droplets occurs in the cytoplasm of mouse oocytes during maturation, regardless of in vivo or in vitro maturation, and that such the change in the inclusion is not related to nuclear maturation. (Reprod Med Biol 2004; 3: 231-236).