Doxorubicin affects the cardiac muscarinic system in the rat.

During the study on the mechanism of doxorubicin-induced cardiotoxicity, we observed that a long incubation (4 hr) with doxorubicin reduced the maximal negative inotropic effects of a muscarinic receptor agonist, carbachol. The mechanism responsible for this doxorubicin-induced reduction of the efficacy of carbachol was examined in isolated guinea pig hearts. In isolated left atrial muscle preparations, 1 hr incubation with 100 microM doxorubicin caused a parallel right-ward shift of the concentration-response curves for carbachol, but a longer (4 hr) incubation with this agent (30, 100 or 200 microM), caused a significant reduction of the magnitude of the negative inotropic effect of carbachol in addition to the concentration-dependent parallel right-ward shift. The 4-hr incubation with these concentrations of doxorubicin also reduced the maximal negative inotropic effect of an adenosine A1 receptor agonist, R-phenylisopropyl adenosine (R-PIA), without affecting the potency of this agonist. Doxorubicin (1 to 100 microM) reduced [3H]quinuclidinyl benzilate (QNB) binding in a concentration dependent manner, but failed to alter [3HIR-PIA binding. The decrease in the magnitude of the maximal negative inotropic effect by doxorubicin was caused by changes in the muscarinic system at steps common to the transduction of muscarinic and adenosine A1 receptor mechanisms.     

Horizontal transmission and host-virulence attenuation of totivirus in violet root rot fungus Helicobasidium mompa

Monokaryotic strains of Helicobasidium mompa were used as vectors of a mycovirus between various H. mompa isolates to examine the transmissibility of one of the mycoviruses, totivirus (HmTV1–17 virus) in the hypovirulent isolate V17 of H. mompa. The isolates that acquired HmTV1–17 virus were also examined for any alteration in the virulence. Twelve dikaryotic isolates of H. mompa, belonging to 11 mycelial compatibility groups (MCGs) and being mycelially incompatible with isolate V17, were used as recipients of HmTV1–17 virus. Two monokaryotic isolates that were mycelially incompatible with isolate V17 and all of the recipients were also used as vectors of HmTV1-17 virus between isolate V17 and the recipients. When isolate V17 and recipients were directly paired on plate media, HmTV1-17 virus was transmitted from isolate V17 into 2 of the 12 recipients (i.e., 2 of the 11 MCGs). Two monokaryotic strains were paired with isolate V17, and the monokaryotic strains that acquired HmTV1-17 virus were then used as new virus donors. When the monokaryotic strains containing HmTV1-17 virus were paired with the 12 recipients, HmTV1-17 virus was transmitted into 7 of the 12 recipients from the monokaryotic strains (i.e., 7 of 11 MCGs). Based on these results, we concluded that monokaryotic strains could act as vectors to transmit HmTV1-17 virus into H. mompa isolates. When four of the H. mompa isolates that acquired HmTV1-17 virus were used to inoculate apple rootstock Malus prunifolia, the virulence of all of the isolates was attenuated from that of their parental isolates. Moreover, because the DNA fingerprints of the fungal isolates that acquired HmTV1-17 virus were the same as those of their parental isolates, the infection with HmTV1-17 virus is considered the cause of virulence attenuation of H. mompa.     

Antagonism of medetomidine sedation by atipamezole in pigs.

The efficacy of atipamezole as a medetomidine antagonist was evaluated in pigs. The atipamezole doses (intramuscularly) were 80, 160, 320 and 480 micrograms/kg of body weight, which were one, two, four and six times higher than the preceding medetomidine dose (80 micrograms/kg, intramuscularly). Atipamezole effectively reversed medetomidine-induced sedation, and the optimal action was seen at doses of 160 and 320 micrograms/kg. Recovery from sedation was quick and smooth, and adverse effects such as hyperactivity or tachycardia were minimal with either dose.     

Bovine Posterior Pituitary Extract Stimulates Prolactin Release from the Anterior Pituitary Gland In Vitro and In Vivo in Cattle

It has been reported that the posterior pituitary (PP) gland contains a potent, unknown prolactin (PRL)-releasing factor (PRF) in rats. PRFs are assumed to be produced in neurones located within the hypothalamus, and to be peptidergic in nature. However, little is known about PRFs in domestic animals. To characterize the PRF in the PP of domestic animals, the present study examined the PRL-releasing activity of an acidic extract from bovine PP (bPP) in vitro and in vivo in cattle. First, the PRL-releasing effect of bPP extract was compared with that of PRL-releasing peptide (PrRP), and thyrotropin-releasing hormone (TRH) from cultured bovine anterior pituitary cells. The extract significantly increased PRL concentrations in the culture medium, at doses of 0.002 and 0.02 eq./ml (one eq. is the PP extract from one animal), compared with the control (p < 0.05). PrRP failed to stimulate the release of PRL. TRH significantly increased PRL concentrations in the culture medium, at doses from 10(-9) to 10(-7) M, compared with the control (p < 0.05). The rate of increase in the PRL concentration, by 0.02 eq./ml bPP extract, was significantly greater than that in TRH (p < 0.05). Secondly, plasma PRL responses to the intravenous (i.v.) injection of bPP extract (0.5 eq./head), PrRP [3.59 mug/kg body weight (BW)], TRH (1 mug/kg BW), and a dopamine receptor antagonist (sulpiride, 0.1 mg/kg BW), were examined in calves. PrRP failed to stimulate PRL release; however, plasma PRL increased immediately following the injection of bPP extract, TRH and sulpiride. The PRL-releasing effect of i.v. injections of TRH and sulpiride was more potent than that of bPP extract. Finally, plasma PRL responses to the intra-hypothalamic injection of bPP extract were examined in calves. The intra-hypothalamic infusion (arcuate nucleus) of 0.0625 eq./head of bPP extract strongly stimulated PRL release in calves (p < 0.05). The present results show that PP contains a physiologically potent PRF in cattle.     

Cyclopedic protein expression analysis of cultured canine mammary gland adenocarcinoma cells from six tumours

We characterised cultured canine mammary gland adenocarcinoma cells by exhaustive step protein expression analysis to identify factors associated with tumour progression or metastasis of canine mammary gland tumour. Cultured adenocarcinoma cells derived from a total of 3 primary and 3 metastatic lesions from 3 dogs (CHMp/m, CIPp/m and CNMp/m, where CHM, CIP, and CNM indicate the 3 animals) were used in this study. The expression of 24 proteins reported to be related to tumourigenesis or malignancy of human breast cancers were examined by Western blot analysis using 24 antibodies. The expression of sialyl Lewis X [sLe(x)] was only observed in CHMm cells, which were derived from pleural effusion. This expression was further confirmed by immunohistochemistry. The levels of some factors, such as 14-3-3sigma, cyclinD1 and Rb, differed among cells or between the primary and metastatic cells in the pair. Though the difference in their expression was not consistent within the cells from primary and metastatic origin, this characterisation should provide useful information for further molecular analysis of these cultured cells. Since some of the factors, such as sLe(x), 14-3-3sigma, cyclinD1 and Rb, showed different levels of expression in the pair, these cultured cells might be meaningful tools for clarification of distant metastasis in canine mammary gland tumours.     

Effects of perineural capsaicin treatment on compound action potentials of superior laryngeal nerve afferents in sevoflurane-anesthetized dogs

Effects of perineural capsaicin (CAPS) treatment on compound action potentials of the superior laryngeal nerve (SLN) afferents were studied in 6 sevoflurane-anesthetized dogs. Perineural CAPS (100 microg/ml) to the bilateral SLNs reduced (P<0.01) the peak and integral amplitudes of the C-wave of the compound action potential. By contrast, the perineural CAPS had no effect on the A-wave component (P>0.05). Removal of the perineural CAPS recovered the C-wave to pretreatment level. The perineural CAPS treatment selectively blocks C-wave compound action potentials of the SLN afferents, providing a useful tool for studies of laryngeal C-fibers in respiratory physiology.     

The effect of motilin on the regulation mechanism of intestinal motility in conscious horses

Laparotomy was performed on seven thoroughbreds to attach a force transducer to the proximal jejunum, distal jejunum, and ileum, as well as to the serous membrane of the cecum. Following observation of intestinal motility in conscious horses, they were intravenously injected with motilin (0.6 microgram/kg) to examine its effect on intestinal motility. Strong contractions peculiar to horses were observed in small intestine. Further, motilin caused strong contractions in the proximal jejunum. The results suggested the involvement of motilin in the regulation mechanism of intestinal motility.     

Biological effect of tyrosine kinase inhibitors on three canine mast cell tumor cell lines with various KIT statuses

Tyrosine kinase inhibitors (TKIs) can be important in the treatment of canine mast cell tumor (cMCT). Meanwhile, some TKIs have been identified as substrates for ABCB1. The inhibitory effect of four TKIs (axitinib, imatinib, masitinib, and vatalanib) for proliferation and phosphorylation of c-Kit receptor as well as the expression and function of ABCB1 were investigated in three cMCT cell lines (HRMC, VIMC1, and CMMC1). The IC(50) values of the TKIs in HRMC, the only cell line with wild-type KIT, were clearly higher than those in CMMC1 and VIMC1. In HRMC and CMMC1, both the growth and phosphorylation of c-Kit receptor were suppressed proportionally by the TKIs. VIMC1 required higher concentrations for the inhibition of c-Kit receptor phosphorylation than those in cell growth. The treatment with cyclosporine increased the effects of the TKIs on VIMC1 since ABCB1 was expressed in VIMC1. The results indicated that cMCT cell lines harboring wild-type KIT had lower sensitivity to TKIs. The growth of VIMC1 was seemingly reduced by TKIs through the inhibition of other tyrosine kinases than c-Kit receptor. There was little influence of ABCB1 on TKI effects to the proliferation of VIMC1. These results will be helpful to understand the different sensitivity to TKIs in cMCT patients.     

Time-course comparison of pulmonary inflammation induced by intratracheal instillation of four different nickel oxide nanoparticles in male Fischer rats

Occupational exposure to nickel oxide (NiO) is an important cause of respiratory tract cancer. Toxicity is known to be associated with the dissociated component, i.e. nickel (II) ions. To address the relationship between physicochemical properties, including solubility in artificial lysosomal fluid, of NiO and time-course changes in the pulmonary response, we conducted an intratracheal instillation study in male Fischer rats using four different well-characterized NiO products, US3352 (NiO A), NovaWireNi01 (NiO B), I small particle (NiO C), and 637130 (NiO D). The NiOs were suspended in purified water and instilled once intratracheally into male F344 rats (12 weeks old) at 0 (vehicle control), 0.67, 2, and 6 mg/kg body weight. The animals were euthanized on days 3, 28, or 91 after instillation, and blood analysis, bronchoalveolar lavage fluid (BALF) testing, and histopathological examination were performed. The most soluble product, NiO B, caused the most severe systemic toxicity, leading to a high mortality rate, but the response was transient and surviving animals recovered. The second-most-soluble material, NiO D, and the third, NiO A, caused evident pulmonary inflammation, and the responses persisted for at least 91 days with collagen proliferation. In contrast, NiO C induced barely detectable inflammation in the BALF examination, and no marked changes were noted on histopathology. These results indicate that the early phase toxic potential of NiO products, but not the persistence of pulmonary inflammation, is associated with their solubility.