To clarify whether apoptosis is involved in doxorubicin (DXR)-induced testicular toxicity and to identify the target germ cell type, adult Sprague-Dawley rats were treated with a single intravenous dose of DXR (8 or 12 mg/kg) and euthanized at 3, 6, 12, 24, and 48 h subsequently. Histologically, germ cell degeneration was first found 6 h after dosing in meiotically dividing spermatocytes and early round spermatids of seminiferous tubules at stage 1, and subsequently observed in spermatogonia at stages I-VI showing ultrastructural characteristics of apoptosis. Coincident with the appearance of morphological changes, degenerating germ cells were shown to be undergoing apoptosis as revealed by in situ terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL). The frequency of TUNEL-labeled germ cells increased in a stage- and cell type-specific manner, the peak of frequency gradually progressing from stage I of seminiferous tubules to later stages with time after dosing, suggesting that the damaged germ cells, especially spermatogonia, gradually underwent the processes leading to apoptosis. DNA laddering on gel electrophoresis was apparent 24 and 48 h after dosing. The results demonstrate that apoptosis plays an important role in the induction of testicular toxicity caused by DXR with meiotically dividing spermatocytes and type A and intermediate spermatogonia as highly vulnerable target cells.

Effects of heat shock transcription factor 1 (HSF1) gene on the regrowth of atrophied mouse soleus muscles were studied. Both HSF1-null and wild-type mice were subjected to continuous hindlimb suspension for 2 wk followed by 4 wk of ambulation recovery. There was no difference in the magnitude of suspension-related decrease of muscle weight, protein content, and the cross-sectional area of muscle fibers between both types of mice. However, the regrowth of atrophied soleus muscle in HSF1-null mice was slower compared with that in wild-type mice. Lower baseline expression level of HSP25, HSC70, and HSP72 were noted in soleus muscle of HSF1-null mice. Unloading-associated downregulation and reloading-associated upregulation of HSP25 and HSP72 mRNA were observed not only in wild-type mice but also in HSF1-null mice. Reloading-associated upregulation of HSP72 and HSP25 during the regrowth of atrophied muscle was observed in wild-type mice. Minor and delayed upregulation of HSP72 at mRNA and protein levels was also seen in HSF1-null mice. Significant upregulations of HSF2 and HSF4 were observed immediately after the suspension in HSF1-null mice, but not in wild-type mice. Therefore, HSP72 expression in soleus muscle might be regulated by the posttranscriptional level, but not by the stress response. Evidence from this study suggested that the upregulation of HSPs induced by HSF1-associated stress response might play, in part, important roles in the mechanical loading (stress)-associated regrowth of skeletal muscle.

Spontaneous hyperglycemia, glycosuria, hypoinsulinemia, and glucose intolerance were observed in some WBN/Kob rats, at about 9 months of age, and in all at the age of 17 months. Females did not present this pathology. Histopathologic examination of the pancreas revealed severe changes in male rats at the age of 3 months. Between 3 and 6 months of age a distinct infiltration of inflammatory cells was found around islets and among adjacent acinar cells. At the same time, marked fibrosis was seen around the pancreatic ducts and blood vessels. With advancing age the fibrous tissue gradually invaded extensive areas of the pancreas where also the islets became involved in fibrotic degeneration. At 17 months of age and later, an obvious decrease in islet number and size (less than 50 mu in diameter) was observed, even in relatively unaffected areas of the organ. Frequent bilateral cataracts began to appear at about 15 months of age. Opacities were first observed in the periphery of the lens, then increased rapidly in intensity and extended centripetally. Nineteen-month-old male rats were hypersensitive to exogenous insulin, but showed no significant decrease in blood glucose level when treated with oral tolbutamide. These results suggest that these rats suffered from a decreased insulinogenic response.

No abstract

To determine if hemizygous transgenic mice carrying the human c-Ha-ras gene (CB6F1-Tg Hras2 mice (Hras2 mice)) are susceptible to the carcinogenic potential of known murine carcinogens, male and female Hras2 mice and their non-transgenic CB6F1 littermates (non-Tg mice) were each given a single intraperitoneal injection of 60 mg of vinyl carbamate (VC)/kg body weight or saline (vehicle control) and monitored for 16 wk without further treatment. At necropsy, grossly visible tumors were fixed for histopathologic diagnosis and, when of sufficient size, portions were frozen for subsequent molecular analysis. Nine of 31 male and nine of 29 female Hras2 mice treated with VC died within 16 wk as a result of lung tumor burden. At the termination of the study, lung tumors (alveolar-bronchiolar epithelial neoplasms and hemangiosarcomas) and focal alveolar-bronchiolar hyperplasias were present in both sexes of Hras2 and non-Tg mice treated with VC; there were significantly more proliferative lung lesions in Hras2 than non-Tg mice. Splenic hemangiosarcomas and squamous cell tumors of the forestomach were induced in male and female VC-treated Hras2 mice but not in VC-treated non-Tg mice. Polymerase chain reaction-single-strand conformation polymorphism analysis and DNA sequencing of the induced lung tumors revealed point mutations at codon 61 of the transgene in two of 29 lung tumors (one of 16 in males and one of 13 in females) from VC-treated Hras2 mice; no mutations in murine Ki-ras were found in these tumors. Point mutations at codons 12 and 61 of the murine Ki-ras gene were observed, however, in one of 10 and six of 10 lung tumors respectively, from VC-treated non-Tg mice. These findings indicate that Hras2 mice are highly sensitive to pulmonary neoplasms and splenic and lung hemangiosarcomas after treatment with VC. The molecular analyses suggest that point mutations of the transgene and the murine Ki-ras gene do not play a major role in VC induction of pulmonary neoplasms in these transgenic mice.