[Perinatal mortality of puppies after caesarean section caused by intrauterine infection]. / Tod eines Wurfs Hundewelpen nach Sectio caesarea aufgrund einer intrauterinen Infektion.

Perinatal mortality in dogs and cats is relatively high. Whereas the death of puppies within the first 3 weeks of life is commonly assumed to be due to infectious causes, peracute death of neonates immediate- ly after parturition or caesarean section results in a high potential for conflict between owner and veterinarian. In this respect, the owner often postulates a wrong anaesthetic regime or a too prolonged duration of surgery. This case report, however, clearly shows that also in the case of immediate perinatal death, infectious causes - e.g. due to intrauterine infection - have to be taken into consideration and that pathological, virological and bacteriological post-mortem examinations of puppies is an important procedure to identify the reason for perinatal death.

Dose-response relationship of fibrous dusts in intraperitoneal studies.

The relationship between the number of fibers injected intraperitoneally and the occurrence of peritoneal mesotheliomas in rats was investigated using data from a series of carcinogenicity studies with several fibrous dusts. Based on observed tumor incidences ranging between 10 and 90%, the hypothesis of a common slope of dose-response relationships (parallel probit lines in probit analysis) cannot be rejected. In general, parallelism of probit lines is considered an indication of a common mode of action. Analysis of the shape of the dose-response relationship, with one apparent exception, shows virtually linear or superlinear behavior, i.e., from these data, there is no indication of a decrease in carcinogenic potency of an elementary carcinogenic unit at lower doses.

Results of current intraperitoneal carcinogenicity studies with mineral and vitreous fibres.

The study includes some 50 groups of male or female Wistar rats tested in three series. Except for one untreated group and 3 vehicle control groups, the animals were injected intraperitoneally (i.p.) once or repeatedly with dust suspensions and then examined, after lifetime observation up to 30 months, for tumours in the abdominal cavity. 1 granular dust (silicon carbide), 2 asbestos dusts (crocidolite, tremolite) and 11 vitreous fibre dust samples were administered. 5 of the vitreous fibre types were fine fibre fractions from 4 commercial insulation wools and 1 experimental wool, the others were prepared by milling glass microfibres, which have, per se, a small diameter range. The dosage per rat differed over a wide range in accordance with experience from earlier studies. The lowest dose was 0.04 x 10(9) crocidolite fibres in 0.5 mg dust, and the highest amounted to 20 x 10(9) glass fibres in 1000 mg divided into 40 weekly injections. Two mesotheliomas were found in a total of 395 rats treated with saline or granular silicon carbide (250 or 1000 mg). Eleven fibre dusts produced dose-dependent mesotheliomas at rates of up to 97 %, but the calculated fibre number > 5 micrometers in length required for inducing a 25 % tumour risk differed between the fibre samples tested in the relation of 1 to about 1000. UICC-like crocidolite heads the ranking order; the glass fibre B-01, which possesses a low durability in the body, ends it together with a rather thin sample of glass fibre type B-09. The stone fibre MMVF-21 takes a high place in the ranking order, similar to the tremolite sample. The results correspond to those of earlier i.p. tests.

Differential diagnosis of malignant tumours in the abdominal cavity of rats after intraperitoneal injection of crocidolite or benzo[a]pyrene.

In our investigation (i.p. test), crocidolite and benzo[a]pyrene, both caused a progression from initially reactive, then autonomously transformed proliferation of myofibroblasts and undifferentiated mesenchymal cells to malignant, multidirectionally differentiated (desmin and ED-1 positive) fibro-histiocytic tumours. Immunohistochemically these tumours showed no morphological characteristics (for example co-expression of vimentin and keratin in spindle-shaped tumour cells) of human asbestos-associated malignant mesotheliomas. On the other hand many tumour cells induced by crocidolite and benzo[a]pyrene had an ultrastructural appearance resembling fibroblasts and myofibroblasts. These have been demonstrated in only a few desmoplastic and sarcomatous mesotheliomas in human beings. None of the tumours revealed the typical ultrastructural features of epitheloid or transitional mesotheliomas. Apparently, both carcinogenic substances induce the transformation of undifferentiated pluripotent mesenchymal cells in rat peritoneum, regardless of their localization in the submesothelial compartment or perivascular connective tissue (preferentially after crocidolite application) or in the connective tissue pseudocapsule of major benzo[a]pyrene containing beeswax/tricaprylin depots in the mesometrium and mesenterial fatty tissue. In this way asbestos fibres in this animal experiment do not seem to induce an arrest in differentiation of intermediate or immature mesothelial cells as supposed formerly, but rather affect undifferentiated mesenchyme cells and myofibroblasts. This is an explanation for the immunohistochemical expression of markers of muscular differentiation in these tumour cells, which is known to occur in human malignant fibro-histiocytic tumours. If supplementary immunohistochemical investigations with different keratin antibodies also fail to confirm the mesothelial differentiation of the tumours induced in our i.p. test, the decision to call them "mesotheliomas" should be reconsidered. Further immuno-transmission-electron microscopical investigations with intermediate filament or macrophage antibodies are needed to clarify whether the term malignant "fibrohistiocytic sarcoma", "mesenchymoma" or "mesothelioblastoma" would be more correct from the morphological point of view.

Reconstitution of photophosphorylation in EDTA-treated thylakoids by added chloroplast coupling factor 1 (ATPase) and chloroplast coupling factor 1 lacking the delta subunit. Structural or functional?

Upon EDTA treatment thylakoids lose the chloroplast coupling factor 1 (CF1) part of their ATP synthase, CF0CF1, this exposes the proton channel, CF0. The previously established ability of the CF1 subunit delta to block the proton leak through CF0 prompted us to study (a) the ability of complete CF1 and, for comparison, CF1 lacking the delta subunit to block proton leakage and thereby to reconstitute structurally some photophosphorylation activity of the remaining CF0CF1 molecules and (b) their ability to form functional enzymes (functional reconstitution). In order to discriminate between activities caused by added CF1 or CF1(-delta) and remaining CF0CF1, the former were inhibited by chemical modification of subunit beta by N,N'-dicyclohexyl carbodiimide (DCCD) and the latter by tentoxin. We found that added CF1 acted both structurally and functionally while added DCCD-treated CF1 (DCCD-CF1) acted only structurally. In contrast to previous observations, CF1(-delta) and DCCD-CF1(-delta) also acted structurally although the reduction of proton leakage was smaller than with DCCD-CF1. Hence there was no functional reconstitution without subunit delta present. Previous studies indicated that only a small fraction of exposed CF0 is highly conducting and that this small fraction is distinguished by its high affinity for added CF1. The results of this study point rather to a wider distribution of CF0 conductance states and binding affinities.