Effects of the oral antidiabetic repaglinide on the reproduction of rats.

Repaglinide (CAS 135062-02-1), a biguanide, is an orally available insulin secretagogue (beta-cell stimulant) and has been developed for the treatment of Type II diabetes. The developmental toxicity of the compound was investigated in rats. The effects on fertility, on embryo- and fetogenesis and on peri- and postnatal development were investigated. In a 'fertility study' 24 males were treated with 0, 1, 30, 300 mg/kg for 10 weeks prior to mating and during mating, and 24 females with 0, 1, 30, 80 mg/kg for 4 weeks prior to mating until gestation day 22 (hysterectomy group) or through gestation day 22 until postnatal day, i.e. lactation day 21 (littering group). In a 'teratogenicity study' with a hysterectomy group and a littering group included, 36 females were treated with 0, 0.5, 5 and 80 mg/kg from gestation day 7-16. In a 'peri-postnatal study' with a cross-foster group included 23 females were treated in the core study with 0, 0.5, 5, 30 and 80 mg/kg from gestation day 16 to lactation day 21 and in the cross-foster group 18 females with 0 and 80 mg/kg from gestation day 16 to lactation day 21. In a 'supplementary study' with five treatment windows 13 females each were treated with 80/30 mg/kg from gestation day 1-5 (W 1), gestation day 6-16 (W 2), gestation day 17-22 (W 3), lactation day 1-14 (W 4) and lactation day 15-21 (W 5). Effects of repaglinide on fertility, implantation, early and late embryogenesis, fetogenesis, birth and postnatal development including fertility of the offspring were investigated. In the 'fertility study' the NOTEL (no toxic effect level) for males was estimated to be 1 mg/kg and for females 30 mg/kg. In the 'teratogenicity study' the maternal NOTEL was 0.5 mg/kg as it was in the 'peri-postnatal study' 5 mg/kg. Food consumption and body weight gain of females were significantly reduced at the beginning of the respective treatment periods of the 'supplementary study' indicating a strong reaction of the dams to the treatment underlined by the death of individual animals (W 3, W 4 and W 5). Offspring survival during the last trimester of pregnancy and during lactation was affected in the 'fertility study' and in the 'peri-postnatal study' after 30 and 80 mg/kg and in the 'supplementary study' slightly in W 3 and more pronounced in W 4 and W 5. Changes of the skeleton in the extremities of the offspring were observed in all studies where the animals were exposed to repaglinide during late pregnancy (i.e. after completion of organogenesis) and/or lactation. At radiography the skeletal alterations comprised deformities of the coracoid process and acromion process, of the proximal humeral epiphysis, and of the epiphysis distalis and the condylus distalis of the femur. Deltoids of the humerus showed a slight increase of height and a length reduction. The radius and ulna were slightly bent. The most marked effects and the highest incidence were induced during the first half of lactation (W 4). As age of offspring increased the changes were more pronounced and occurred with a higher incidence. Correspondingly, ash weight, calcium, magnesium and phosphorus content of bones were reduced, but the proportions remained constant. Histopathological examination (supplementary study) showed that small fibrotic foci were formed in the area of dislocation of parts of the epiphyseal plate and that the remaining hyaline cartilage was thinner than normal (W 3, W 4 and W 5). Additionally, the longitudinal axis of the diaphysis juxtaposed to the growth zone was markedly bent, becoming convex to the lateral side. The studies clearly demonstrated that long bone development was not impaired during embryogenesis and early fetogenesis but after completition of organogenesis exclusively, indicating that repaglinide was not teratogenic. Effects of repaglinide were clearly effects on growth. The effects seen in all studies only occurred at excessively high plasma concentrations which will not be reached at human therapeutic dos

Comparative cardiac toxicity of the i.v. administered benzimidazole pyridazinon derivative Pimobendan and its enantiomers in female Beagle dogs.

The new positive-inotropic and vasodilatating drug Pimobendan (racemate), 4,5-dihydro-6-[2-(4-methoxyphenyl)-1H-benzimidazole-5-yl]-5-methyl-3 (2-H)-pyridazinone, and its enantiomers were investigated with regard to their cardiotoxicity in young adult female Chbb: Beagle dogs. The racemate and the (-)-isomer (eutomer) were intravenously injected once daily for 4 consecutive weeks at doses of 0.25, 0.75 and 2.25 mg/kg, and the (+)-isomer (distomer) at doses of 0.75, 2.25 and 6.75 mg/kg, respectively. Clinical signs, hematological, clinico-chemical, ophthalmologic and electrophysiological parameters were monitored. Plasma concentration-time profiles of the parent compound and the major metabolite UD-CG 212 were established on day 1 and in week 4 using an HPLC assay. Partial areas under the curves from 0.08 h to 1 h (AUC0.08-1 h) as well as the plasma concentration at time point 0.5 h/C0.5 h) were used for statistical calculations. Necropsy and histopathologic examination were performed after completion of the treatment period. Reduction of the blood pressure occurred already at low dosages of the racemate and the eutomer, but only in high dose distomer-treated animals. A tendency to tachycardia developed only in high dose females receiving the racemate. Consequently, with respect to the pharmacological effects and the adverse events, the racemate is equivalent to the eutomer. Plasma concentrations of parent compound and metabolite were dose-linear for racemate, eutomer and distomer within the dose range 0.25-2.25 mg/kg.d at both time points. There were no significant effects of form or repeated administration. A moderate increase of AUC0.08 1 h and C0.5 h could be seen on day 23 for the distomer indicating a stereoselektive metabolism of the latter. Histologic changes of the valvular and parietal endocardium being termed jet lesion were observed after administration of the racemate (> or = 0.75 mg/kg.d) and the eutomer (> or = 0.25 mg/kg.d) at distinctly lower doses than after the distomer (> or = 2.25 mg/kg.d). Furthermore, extent and severity of the morphologic lesions were found to be higher in dogs exposed to the racemate or the eutomer than in those receiving the distomer. The results gave evidence that the so-called cardiotoxicity by Pimobendan in dogs resulted from the exaggerated pharmacodynamic effect but not from the chemical nature of the compound per se. They corroborate also the previously raised assumption that the exaggerated pharmacodynamic activity of cardiotonic compounds in the broadest sense accounts for their morphologic adverse effects in experimental animals.

Social isolation modifies the response of mice to experimental Mengo virus infection.

To investigate the effects of social isolation on host resistance male mice were housed either individually (IH) or in groups of four or five (GH). All animals were infected with MengoM,L virus. Incubation time (INCUB), duration of illness (ILL), death rate (DR), histopathological changes, and serum corticosterone levels (CORT) were recorded. First, the effect of IH starting 4 days prior to infection was studied in 5 different inbred strains. Next, the effect of different IH length was examined, and the role of T-cells was investigated by comparing euthymic (+/+) and athymic (nu/nu) NMRI mice. Finally, the effects of the infection on CORT in IH and GH mice were compared in C57BL/6 mice. The major findings were: 1. IH significantly increased ILL in all but the DBA/2 strain, whereas DR was not affected except in C57BL/6. 2. Longer IH (starting 35 [DBA/2] or 10 [NMRI] days prior to virus inoculation) significantly shortened INCUB and prolonged ILL, but IH starting on the day of virus inoculation [DBA/2] significantly prolonged INCUB and shortened ILL. 3. NMRI nude mice exhibited an unaltered DR accompanied by a tremendously prolonged INCUB. 4. Investigations in C57BL/6 mice revealed a significant rise of CORT after infection. This increase was higher in IH compared to GH mice. It is suggested that IH attenuates T-cell mediated inflammatory processes and/or increases macrophage activation, which in turn results in a prolonged course of the disease.

[2-Amino-oxazoles as potential H-bonding agents in virostatic research. 4. Pharmacokinetics and pharmacologic-toxicologic profile of 2-guanidino-4,5-dipropyloxazole hydrochloride]. / 2-Amino-oxazole als potentielle H-Brückenbildner in der Virostatika-Forschung. 4. Mitteilung: Pharmakokinetik und pharmakologisch-toxikologisches Wirkprofil von 2-Guanidino-4,5-dipropyloxazol-hydrochlorid.

Out of the group of 2-amino-oxazoles 1 was found to be the most potent antiviral compound. Following p.o. or s.c. administration to rats, the 14C-labeled 1 was quickly and completely absorbed. The TRA was eliminated mainly via the kidneys and the liver with half-lives between 32 and 42 h. The acute pharmacodynamic effects of 1 were decrease of blood pressure, bradycardia, and inhibition of both gastric emptying and acid secretion. On smooth muscles spasmolytic and alpha-anti-adrenergic actions were predominant. After single administration the following MTD's were determined: 30 (mouse), 20 (rat), 10 mg/kg i.v. (pig), and 500 (mouse, rat), greater than 100 mg/kg p.o. (pig), respectively. In a subchronic toxicity study in rats, oral doses of 1 between 15 and 240 mg/kg given daily for 4 weeks were tolerated without any severe alterations related to the drug.

Peculiarities of the liver histology of laboratory rodents.

Although the general liver morphology is similar in all mammals, there are some structural features in apparently healthy laboratory rodents. These peculiarities are known to be influenced by a great variety of endogenous and exogenous factors. Incidence, intensity, development and disappearance of such elements as extramedullary haemopoiesis, polyploidy, intranuclear and intracytoplasmic inclusions depend markedly upon genetics, age, hygienic condition, hormonal regulation and nutrition of the animals. It is concluded from this short review that the term "normal histology" should only be understood as being relative and that it may only be applied to a given, well defined animal population held under well defined conditions.

[Acute and subacute toxicity of antineoplastic Pt(II) and Pt(IV) coordination compounds in laboratory rodents]. / Akute und subakute Toxizität antineoplastisch wirksamer Pt(II)- und Pt(IV)-Koordinationsverbindungen bei Labornagern.

After single i.v. administration of cis-diammine-platinum(II)-lactate cis-diammine-platinum(II)-lactate, L cis-diammine-platinum(II)-dilactate trans-dihydroxy-cis-dichlorodiammine-platinum(IV), the LD50 values have been calculated to range between 80 and 130 mg/kg in mice, and between 22 and 45 mg/kg in rats. The LD50 of cis-DDP amounted to 17 mg/kg and 6.6 mg/kg, respectively. Likewise, the compounds have been found to be about 3 to 5 times less toxic than the standard cis-DDP when administered daily for 5 consecutive days. Since the kidneys, the bone marrow, the lymphatic tissue and the intestinal tract have been proved to be the main target organs, the profile of the toxic action of the Pt(II)-complexes seems to be similar to that of cis-DDP. Additionally, the Pt(IV) compound has been found to be toxic to the pancreas, the liver and the salivary glands. With regard to the antineoplastic activity the more soluble lactates of cis-DDP showed a smaller therapeutic index compared to cis-DDP.

Biological characterization of three new spontaneous mouse lymphomas and comparison with the leukemia P388.

Three spontaneous lymphomas of 23- to 24-month-old (AB/Jena X DBA/2 Jena)F1 females were serially transplanted into syngeneic hosts. They were histologically classified as malignant lymphoblastic lymphomas (ABDt2 and ABDt5) and as a malignant lymphoma of histiocytic type (ABDt6). All lymphomas disseminated into the liver, spleen, and pancreas, whereas ABDt2 and ABDt5 additionally infiltrated the bone marrow and leptomeninx. None of the tumors showed a leukemic growth form, but extreme granulocytosis was observed in leukemia P388-bearing mice. Since the lymphomas ABDt2 and ABDt5 expressed T-cell differentiation antigens Ly-1, Ly-2, and Ly-3, they are thought to be of T-cell origin. On the contrary to the lymphocytes of parental mouse strain ABDt2 and ABDt5 cells reacted with anti H-2.23 allosera. All tumors have been found to be sensitive to at least 5/7 clinically used anticancer drugs. But only ABDt2- and P388-bearing mice survived longer than 60 days after treatment with the potent anticancer drug 1,4-benzoquinone-guanylhydrazone-thiosemicarbazone (ambazone). Successful chemotherapy of both tumors was accompanied with resistance of the hosts against the second transplant of the same tumor. Summarizing the characteristics of the newly established transplantation tumors it is concluded that they can be recommended as screening models in the search for new antineoplastic agents.

Toxicological studies with recombinant hirudin.

After daily administration of 1 mg/kg over a period of 4 weeks, hirudin did not influence growth and general behaviour of the animals. There was no indication of treatment-related effects on the liver and the kidneys, on number and function of thrombocytes, on number and differentiation of white cells or on the erythrocytic system. Haemorrhagic complications did not occur. Formation of antibodies was not detectable. Histopathological changes due to application of r-hirudin were not found. LD50 is greater than 50 mg/kg body weight for intravenous application.

Dynamic model of the pathogenesis of Mengo virus infection in mice.

A mathematical model of the pathogenesis of experimental Mengo virus infection in mice has been developed and fitted using kinetic data of both virus multiplication in different organs and mortality. The behaviour of the model proved to be bistable. In contrast to the widely accepted hypothesis that an acutely virus-infected host dies when virus replication has attained a critical level in the main target organ, the present results showed the following: the maximum virus titre in brain, the main target organ, has been reached already 24 hr post infection (p.i.) but the animals began to die since 60 hr. Hence, it was postulated and confirmed by a good model fit to the experimental data that the so-called AUC (area under the curve) of the virus multiplication kinetics may be a critical quantity. From this finding a hypothesis was deduced assuming that in the presence of high amounts of the virus the antiviral effect of IFN wanes with time. Since this process accounts for death, it may be a potential target of antiviral therapy.

Synergistic action of quercetin and murine alpha/beta interferon in the treatment of Mengo virus infection in mice.

ABD2F1 mice were infected intraperitoneally (i.p.) or intranasally (i.n.) with Mengo or Sindbis virus and treated with either crude murine alpha/beta interferon (MuIFN-alpha/beta) or quercetin, or both. MuIFN-alpha/beta given i.p. or intramuscularly (i.m.) 1-3 h before the infection had a dose-dependent protective effect regardless of the route of administration. When given after the infection, IFN did not show any effect. Oral quercetin, capable of protecting cardio, i.e. Mengo virus-infected mice, failed to show antiviral efficacy in Sindbis virus-infected animals. Of various combinations of quercetin and MuIFN-alpha/beta, a certain well defined regimen resulted in a significant enhancement of protection in Mengo, but not Sindbis, virus-infected mice. A marginally effective treatment regimen of quercetin (20 mg/kg, given 12 h before Mengo virus infection, and 10 mg/kg given both 1 h before and 12 h after infection) potentiated the activity of a single dose of MuIFN-alpha/beta (5000 IU 3 h prior to infection), giving 85-100% survivors compared to 50% for MuIFN-alpha/beta when applied alone (p less than 0.001).

Inhibition by Norakin (triperiden) of Sindbis virus infection in mice.

Intranasal (i. n.) infection with 10 LD50 of Sindbis virus caused acute encephalomyelitis and death in ABD2F1 mice 3-7 days post infection (p.i.). Histologic lesions were found in the CNS, pancreas. liver, parotid glands, exorbital lacrimal glands, lymphoid organs and kidneys. Repeated oral administration of the anticholinergic anti-Parkinson drug Norakin protected infected animals from death in a dose-dependent manner when treatment was started prior to but not after virus inoculation. The maximum protective effect was achieved when the drug was administered twice daily at doses of 2.5 or 5.0 mg/kg body mass for at least 56 hr; single injections of the full daily dose were ineffective. Daily doses of greater than or equal to 25 mg/kg body mass had a reduced protective effect or failed to prevent mortality. Administration of Norakin up to doses of 300 mg/kg body mass per day to noninfected ABD2F1 mice were tolerated without obvious clinical or histological signs of illness over a period of 104 hr. Replication of sindbis virus in BHK 21/C13 cells was not inhibited by Norakin concentrations up to 10 micrograms/ml. In Mengo virus-infected mice Norakin did not exert any protective effect within the range of 1.25-50.0 mg/kg body mass when treatment started 1 hr before infection and has been continued twice daily over a period of 104 hr.

Failure of high doses of potentially antiviral agents to prevent death in virus-infected mice.

The influence of increasing doses of various potentially antiviral agents on Mengo virus-and Sindbis virus-infected mice was assessed determining death rates and histologic lesions. All drugs given in abundance showed dose-dependent decrease of antiviral activity following the maximum protective effects in either animal model. From the toxicological point of view the antiviral agents in question could be classified into two groups. High doses of tilorone hydrochloride or 10-carboxymethyl-9-acridanone produced toxic effects in both uninfected and virus-infected animals. In contrast, high doses of quercetin, double-stranded ribonucleic acid (dsRNA), 1-ethylisatin-S-n-butylisothiosemicarbazone or Norakin induced no obvious drug-mediated histologic alterations either in uninfected or in virus-infected individuals, but exerted a decreased protection in virus-infected animals. It is suggested that high doses of the compounds of second group adversely affect early host defence in both Mengo virus and Sindbis virus-infected mice.

Toxicity of the alkylating agent bendamustin.

In acute toxicity studies the maximum tolerated dose (MTD), the LD50 and the LD100 of Bendamustin were determined in rats and mice after i.v. and oral administration. In a subchronic study male rats were given Bendamustin for 28 days at oral dose levels of 5, 10, 20 or 40 mg/kg/day. Chlorambucil was used as a standard at dose levels of 1, 5 and 10 mg/kg/day. Bodyweight gain, food and water intake, hematology, clinical chemistry and histopathology were evaluated. With quantitative differences the main target organs for both compounds were the bone marrow, the kidney, the intestine and the lymphatic system. Additionally, Chlorambucil caused a significant atrophy of the testes and a slight atrophy of the pancreas at a dose of 5 mg/kg/day. In conclusion, the data obtained may be used as a base to evaluate the therapeutic range of Bendamustin compared to Chlorambucil for the oral route.

Long term toxicological studies on the progestin STS 557.

The toxicity of 17 alpha-cyanomethyl-17 beta-hydroxy-estra-4, 9-dien-3-one (STS 557) was studied by its oral administration of 0.1, 1.0 or 10.0 mg/kg/day to Wistar rats for six months, and of 0.01, 0.1 or 1.0 mg/kg/day to beagle dogs for six months, respectively. Levonorgestrel at a dose of 1.0 mg/kg/day was used as the standard in the dog study. With respect to the progestational activity of the compound the main target organs were the hypophysis, the reproductive organs and the adrenals. Mammary hyperplasia was observed in dogs treated with STS 557 or levonorgestrel at the dose of 1.0 mg/kg/day, but in no case mammary nodules could be detected. At the dose of 1.0 mg/kg/day STS 557 and levonorgestrel were found to increase the plasma insulin response to i.v. glucose in bitches, but neither the mean blood glucose levels nor the glucose utilization were affected. Moreover, during administration of both steroids to dogs temporary changes in serum concentrations of triglycerides and total cholesterol were noted. The results obtained in rats and dogs from functional and morphological investigations did not reveal any toxic side effects of STS 557 on the liver, the kidneys, the bone marrow or on blood coagulation. The effects on the reproductive organs observed following STS 557 especially in dogs are related to both the hormonal effects of the compound and the specific response of the dog to potent progestagens.