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  • 1
    Electronic Resource
    Electronic Resource
    Mechanistic study on liver tumor promoting effects of piperonyl butoxide in rats (1998)
    Springer
    Archives of toxicology 72 (1998), S. 744-750 
    Details
    ISSN: 1432-0738
    Keywords: Key words Piperonyl butoxide ; Phenobarbital ; Hepatocarcinogenesis promoting mechanism ; Gap junctional intercellular communication ; Cell proliferating activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Piperonyl butoxide, alpha-[2-(2-butoxyethoxy)ethoxy]-4,5-methylenedioxy-2-propyltoluene, is a widely used pesticide-synergist. Recently, results were reported indicating that piperonyl butoxide is a hepatocarcinogen in rat. Since the underlying mechanism was not elucidated, we examined the effects on rat liver cells in detail. For this purpose male F344 rats were administered piperonyl butoxide mixed in the diet at concentrations of 0 (negative control), 0.05, 0.2 or 2% for 2 days, 1, 2, and 4 weeks. As a positive control, phenobarbital was administered to rats for up to 4 weeks as a 0.1% solution in the drinking water. Increased liver weight, centrilobular hepatocellular hypertrophy due to increased smooth endoplasmic reticulum, decreased numbers and areas of connexin 32-positive spots per hepatocyte, and increased cell proliferation were observed in rats treated with 0.2 and 2% piperonyl butoxide. Similar results were obtained for 0.1% phenobarbital treated rats. Hepatocellular necrosis suggestive of hepatotoxicity was also observed in the 2% piperonyl butoxide group. These results indicate that the promoting mechanism of piperonyl butoxide in hepatocarcinogenesis is similar to that of phenobarbital, involving an ability to induce CYP isoenzymes and inhibit gap junctional intercellular communication. In addition, increased cell proliferation following hepatocellular necrosis may also play a role at high doses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002040050569
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  • 2
    Electronic Resource
    Electronic Resource
    Involvement of apoptosis in the rat germ cell degeneration induced by nitrobenzene (1998)
    Springer
    Archives of toxicology 72 (1998), S. 296-302 
    Details
    ISSN: 1432-0738
    Keywords: Key words Nitrobenzene ; Apoptosis ; Testicular toxicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Nitrobenezene (NB) produces germ cell degeneration, especially of spermatocytes in rats. To examine the possible involvement of apoptosis in this process, the extent and nature of nuclear DNA fragmentation after NB dosing were assessed using both terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) and DNA gel electrophoresis, in addition to conventional histological and electron microscopic procedures. Adult Sprague Dawley rats were treated with a single oral dose of NB (250 mg/kg) and euthanized subsequently at 6, 12, and 24 h and 2, 3, 5, and 7 days. The earliest morphological signs of germ cell degeneration in testes were found in pachytene spermatocytes 24 h after dosing. Electron micrographs of degenerating spermatocytes showed marked nuclear chromatin condensation at the nuclear periphery and crowding of cytoplasmic constituents, which are characteristic of apoptosis. Coincident with the appearance of such morphological changes, degenerating spermatocytes contained fragmented DNA as revealed by TUNEL. The presence of DNA laddering, a hallmark of apoptosis on gel electrophoresis, was first apparent and most prominent at 24 h, gradually becoming less detectable. No such changes were observed up to 12 h after dosing or in control animals. These results demonstrated unequivocal involvement of apoptosis in the induction of germ cell degeneration caused by NB.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002040050505
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  • 3
    Electronic Resource
    Electronic Resource
    Ultrastructural changes in motor endplates of the lumbrical muscles of rats induced by a microsomal Ca2+ ATPase inhibitor, 2,5-di(tert-butyl)-1,4-hydroquinone (1997)
    Springer
    Archives of toxicology 72 (1997), S. 115-118 
    Details
    ISSN: 1432-0738
    Keywords: Key words 2 ; 5-di(tert-butyl)-1 ; 4-Hydroquinone ; Ca2+ ATPase inhibitor ; Neurotoxicity ; Ultrastructure ; Motor endplate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Female Wistar rats were treated orally for 5 days with 80 mg/kg body weight of 2,5-di(tert-butyl)-1,4-hydroquinone (DTBHQ), a microsomal Ca2+ ATPase inhibitor. Motor endplates of the lumbrical muscles were examined by light and electron microscopy. There was a decrease in body weight in the treated rats from the first day after administration, and toxic signs appeared after the third day, such as adoption of a prone position, salivation, lacrymation, and an abnormal gait and/or muscle weakness. No remarkable macroscopic or light microscopic changes were noted in the lumbrical muscles as well as other peripheral nerves of hind legs of the treated rats killed 1 day after the last DTBHQ treatment. Ultrastructurally, neurotoxicity characterized by loss of synaptic vesicles and mitochondria in the motor endplates, and by destruction of the motor terminals was detected in the lumbrical muscles of the treated rats. These results strongly indicate that DTBHQ targets the motor endplates in the rat lumbrical muscles and suggest that the resultant damage is responsible for the appearance of neurological signs, such as an abnormal gait and loss of muscle control.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002040050477
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  • 4
    Electronic Resource
    Electronic Resource
    Doxorubicin induces male germ cell apoptosis in rats (1999)
    Springer
    Archives of toxicology 73 (1999), S. 274-281 
    Details
    ISSN: 1432-0738
    Keywords: Key words Doxorubicin ; Apoptosis ; Testicular toxicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract 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 I, 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002040050617
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  • 5
    Electronic Resource
    Electronic Resource
    The relationship between decrease in Cx32 and induction of P450 isozymes in the early phase of clofibrate hepatocarcinogenesis in the rat (1999)
    Springer
    Archives of toxicology 73 (1999), S. 373-380 
    Details
    ISSN: 1432-0738
    Keywords: Key words Clofibrate ; Connexin ; Liver ; Promotion ; P450
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To examine the relationship between the decrease in connexin 32 (Cx32) and induction of P450 isozymes in the early phase of clofibrate hepatocarcinogenesis, a total of 20 male F344 rats were initiated with a single intraperitoneal injection of 150 mg/kg of diethylnitrosamine (DEN) or given the saline vehicle alone and starting 2 weeks later given diet containing 0.18, 0.09, and 0% clofibrate for 6 weeks. All animals were subjected to two-thirds partial hepatectomy at week 3 and killed at week 8. Absolute and relative (ratios to body weight) liver weights were significantly increased in the DEN + clofibrate groups compared with the DEN-alone group. Diffuse hepatocellular hypertrophy with granular cytoplasmic eosinophilia characterized by a marked increase in peroxisomes and smooth endoplasmic reticulum, was observed in the clofibrate treated rats. Induction of cytochrome P450 (CYP) 4A1 and 2B1/2 was noted in the DEN + clofibrate groups, this being most marked in the CYP 2B1 case. Immunohistochemically, positive immunostaining for anti-CYP 4A1 and CYP 2B1 were observed diffusely and centrilobularly, respectively. The numbers and areas of Cx32-positive spots per hepatocyte in the centrilobular areas in the treated rats were significantly decreased in an essentially dose-dependent manner, but no changes were observed in periportal areas. The numbers and areas of foci positive for glutathione S-transferase placental form (GST-P) were decreased in a dose dependent manner in the clofibrate treated groups. These results suggest that the CYP 2B1/2 induction and Cx32 decrease in centrilobular hepatocytes, similarly to those thought to be involved in the hepatic promotion mechanism of phenobarbital, may also play important roles in clofibrate actions in the liver, in addition to its causation of oxidative DNA injury.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002040050676
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  • 6
    Electronic Resource
    Electronic Resource
    Induction and inhibition of testicular germ cell apoptosis by fluoroacetate in rats (2000)
    Springer
    Archives of toxicology 74 (2000), S. 33-39 
    Details
    ISSN: 1432-0738
    Keywords: Key words Fluoroacetate ; Apoptosis ; Testis ; Toxicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Fluoroacetate (FA), an inhibitor of aconitase, is known to lower the intracellular level of adenosine triphosphate (ATP), which recently has been suggested to be a possible determinant of the form of cell death, apoptosis or necrosis. To investigate which form of germ cell death occurs in FA-induced testicular toxicity, adult Sprague Dawley rats were given a single oral dose of FA (0.5 or 1.0 mg/kg) and euthanized at 3, 6, 12, 24, 48, and 72 h thereafter. Germ cell degeneration was histologically first found in early round spermatids at stage I and in spermatogonia at stages II-IV of seminiferous tubules 6 and 12 h, respectively, after dosing. Degenerating spermatogonia exhibited characteristic features of apoptosis as demonstrated by both electron microscopy and in situ terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL), whereas spermatids did not. At the 24 and 48 h time points, degenerating spermatids were continually present and subsequently formed multinucleated giant cells, while the number of degenerating spermatogonia and TUNEL-labeled spermatogonia was drastically and/or significantly decreased compared to those from the control group, indicating that spontaneous male germ cell apoptosis is inhibited. Coincident with these morphological changes, DNA laddering on gel electrophoresis was apparent only 12 h after dosing. The results demonstrate that FA induces either apoptosis or necrosis of male germ cells in the early stage after dosing and subsequently inhibits spontaneous apoptosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002040050649
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  • 7
    Electronic Resource
    Electronic Resource
    Time course of ultrastructural changes and immunoelectron microscopic localization of neurocalcin in motor endplates of the lumbrical muscles of rats given a single administration of 2,5-di(tert-butyl)-1,4-hydroquinone (2000)
    Springer
    Acta neuropathologica 99 (2000), S. 109-116 
    Details
    ISSN: 1432-0533
    Keywords: Key words 2,5-Di(tert-butyl)-1,4-hydroquinone (DTBHQ) ; Wistar rat ; Motor endplate ; Lumbrical ¶muscle ; Neurocalcin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A time-course study of ultrastructural changes and immunoelectron microscopic localization of neurocalcin was performed on motor endplates of the lumbrical muscles of female Wistar rats given a single oral administration of 2,5-di(tert-butyl)-1,4-hydroquinone (DTBHQ) at a dose of 120 mg/kg. Toxic signs such as salivation and muscle weakness of the hind legs appeared from 3 h after DTBHQ administration. No remarkable macroscopic or light microscopic changes were noted in the lumbrical muscles of the treated rats. At the ultrastructural level, neurotoxicity characterized by a decreases or loss of synaptic vesicles and mitochondria was observed after 24 h and at the 1-week time point, nerve endings had disappeared in some of the motor endplates, while many neurite nerve endings suggestive of early stage regeneration were apparent. After 6 weeks, newly formed reinnervated endplates were observed. Immunoelectron microscopically, the synaptic vesicle membranes were heavily labeled for neurocalcin in the control rats, but not at 24 h after DTBHQ treatment. Synaptic vesicle membranes in the DTBHQ group were weakly labeled at 1 week, but strongly at 6 weeks. The results strongly suggest that DTBHQ targets the motor endplates in the rat lumbrical muscles, causing depletion of neurocalcin in the synaptic vesicles followed by their loss.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00007413
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