HFA-134a (1,1,1,2-tetrafluoroethane); lack of oncogenicity in rodents after inhalation.

1. Groups of 60 male and 60 female B6C3F1 mice or HanIbm Wistar rats were exposed to HFA-134a using snout-only inhalation exposure techniques for periods of one hour daily for at least 104 weeks. HFA-134a was delivered directly from cylinders at vapour concentrations of 2500, 15,000 and 75,000ppm for mice and from metered-dose inhalers at vapour concentrations of 2500, 10,000 and 50,000ppm for rats. 2. Intended dosages were achieved. 3. Evidence of absorption was found at each dose level and was dose related. 4. Neither species suffered treatment related effects on survival, clinical signs, body weights, haematology nor on the type, incidence, site or severity of gross lesions. 5. There was no effect of treatment on the type, incidence, site or severity of neoplasms in mice or rats. 6. There were no non-neoplastic findings related to treatment in mice. 7. HFA-134a was considered not to be oncogenic and to provide a safe alternative to chlorofluorocarbons for use in pharmaceutical metered-dose inhalers.

[Potassium hydrogen phosphate induced nephropathy in the dog. I. Pathogenesis of tubular atrophy (author's transl)]. / Die Kaliumhydrogenphosphat-induzierte Nephropathie des Hundes. I. Pathogenese der Tubulusatrophie.

A nephropathy with severe tubular atrophy was observed in Beagle dogs after oral administration of K2HPO4 for 14 or 38 weeks. We describe the complete lysosomal degradation of atrophying tubular epithelial cells. During two experiments of 14 and 38 weeks duration, respectively, a total of 15 Beagle dogs received 0.8 g K2HPO4/kg body weight daily with their food. All dogs were examined clinically at regular intervals. Renal biopsies were taken in the fourth week from beagles of the 14-week study. Results were compared with those of control dogs. At the end of the experiments the animals were killed and necropsies done. Different stains and histochemical reactions were applied to paraffin sections of the kidneys. Acid phosphatase and beta-glucuronidase were found on cryostat sections. Kidneys fixed by perfusion of five Beagles from the 38-week study and three Beagles of the 14-week study, and from five control dogs, were examined electron microscopically. Ultrahistochemically, acid phosphatase was demonstrated. Clinically, the dogs in both experiments vomited, were cachectic, and had elevated creatinine and blood urea nitrogen. Morphologically, qualitatively identical changes were seen, but the renal damage was most marked at 38 weeks. There were disseminated tubular atrophy (usually of the proximal tubules), focal scar tissue and nephrocalcinosis. The following pathogenesis was established for the lesions of the proximal tubule: Tubular atrophy begins with loss of differentiation of epithelial cells. Enzyme histochemistry, ultrahistochemistry and electron microscopy show an increase in autophagic vacuoles and autophagolysosomes. The lysosomal bodies showing fusion enclose large parts of the cytoplasm as the process continues. Complete lysosomal degradation of epithelial cells and extrusion of large lysosomes into the tubular lumen follow. After complete enzymatic digestion of the intratubular detritus, the residue is empty, convoluted and collapsed tubular basement membrane. Atrophic tubular epithelial cells have many organelle-free zones at their base, which contain fine filamentous material resembling that of the basement membrane. The degradation process described here may explain why clinically the urinary sediment contains few cylinders and epithelial cells and why proteinuria decreases significantly toward the end of the experiment. So far, it is not clear whether the tubular basement membrane is synthesized by the tubular cells, by fibroblasts or by both cell types. The presence of basement membrane-like material in tubular epithelial cells and in parietal epithelial cells of the glomerulus favors the view that epithelial cells produce the basement membranes and that increased production of basement membrane-like material is a sign of loss of differentiation.

[Potassium hydrogen phosphate induced nephropathy in the dog. II. Glomerular alterations (author's transl)]. / Die Kaliumhydrogenphosphat-induzierte Nephropathie des Hundes. II. Glomeruläre Veränderungen.

A disseminated atrophy of the proximal tubule accompanies K2HPO4-induced nephropathy in dogs. These pathologic processes cause glomerular changes that pass through different inflammatory stages and terminate in glomerular sclerosis. Experimental animals, design of the experiment and methods have been described [15]. During the 14-week study we determined the amount of urine (24 hours), protein (mg/dl), protein excretion (mg protein/24 hr) and the macro- and microprotein fraction in the urine by SDS-polyacrylamide gel electrophoresis. Clinical examinations were at 15, 66, and 85 days. Beagle dogs treated with 0.8 g K2HPO4/kg body weight developed significant glomerular selective and unselective protienuria. During the experiment the macroproteins in the urine decreased markedly, and at the last examination (day 85) glomerular proteinuria was no longer detectable by electrophoresis. Morphologically, there were only slight glomerular changes in the biopsy material taken at four weeks. Widespread lesions at 14 and 38 weeks were dilatation of Bowman's space, thickening of the basement membrane, increase in mesangial matrix, interposition of non-argentophilic mesangial matrix into the glomerular basement membrane, protein deposits in the mesangium and parietal basement membrane, formation of crescents, shrinkage of the glomeruli with collapse of glomerular tufts, and finally glomerular sclerosis. The parietal epithelial cells contained cytoplasmic areas that were free of organelles and contained microfilamentous and fine-granular material. These areas were close to the capsular basement membrane. Bundles of filaments within parietal epithelial cells had contact with the basement membrane, thus resembling hemidesmosomes. The sequelae of tubular atrophy are retention of glomerular filtrate and dilatation of Bowman's space, followed by compression and shrinkage of the glomerular tufts, and inflammatory processes within the glomerulus. The latter may be characterized as mesangio-sclerosing, mesangio-proliferative, membrano-proliferative, and extra-capillary glomerulonephritis. The decrease of urinary protein excretion towards the end of the experiment may be related to intratubular lysosomal digestion of cellular and amorphous components.

Effects of skin extract on sebaceous gland function in the rat.

The subcutaneous injection of a rat skin extract inhibits sebum excretion. The mitotic rate in the sebaceous glands is reduced. Therefore, a chalone of the sebaceous gland seems to exist. The regulation of sebum excretion is discussed.

Allometric analysis of the atrioventricular heart-valve weights in beagle dogs.

A statistical analysis of atrioventricular heart valve weights of 218 beagle dogs was performed. Applying the allometric function, the correlation between body or heart weight and the weights of the mitral valve, tricuspid valve-angular/parietal leaflet and tricuspid valve-septal leaflet could be described statistically. In the age range between 2 and 81 weeks a significant linear, positive correlation was found for all three parts. The mitral valve and the angular and parietal leaflet of the tricuspid valve show a negative allometry or slower growth rate than body or heart, whereas the septal leaflet grows isometrically. Sex differences were not found. The relevance of such data for the evaluation of certain pathological findings is discussed.

Estrous cycle-controlled cell proliferation in the adrenal cortex of female rats.

In a total of 120 rats the number of 3H-Tdr-labelled nuclei of the adrenocortex was counted during various phases of the estrous cycle. In two separate experiments cyclic variations in the number of DNA synthesizing cells were found. The labelling index of the zona glomerulosa showed a significant maximum in proestrus whereas in zona fasciculata a minimum was revealed in estrus. In the glomerulosa the maximum of labelled cells was followed by a mitotic peak in estrus. Due to very low numbers of labelled cells no rhythm was found in the reticularis. The possible endocrine regulations of this endogenous rhythm of adrenocortical cell replication are discussed.

[Long-term infusion technique via tail vein in unrestrained rat. Technical short communication (author's transl)]. / Zur Technik der Schwanzvenen-Dauerinfusion an der nicht immobilisierten Ratte

A technique is described that allows tail vein infusion in the rat up to several weeks without the risk of pressure necrosis of the tail. By the aid of a simple metallic device the catheter is protected against damage by the animal. Since this armament is well tolerated and the mobility of the rat remains unimpaired, psychic stress is minimized.

Hairs causing pulmonary emboli. A rare complication in long-term intravenous studies in dogs.

Hair particles as arterial lung emboli were an unexpected side effect in a long-term intravenous toxicity study in Beagle dogs. These emboli led to arterial thrombosis and perivascular granulomas or focal interstitial pneumonitis. The emoblic lesions were not severe enough to cause infarction of the lung. This high incidence of hair embolism was related to a moderate solvent-specific chronic dermatitis at injection sites.

[Animal studies on the tolerability of NAB 365 (clenbuterol) (author's transl)]. / Tierexperimentelle Untersuchungen zur Verträglichkeit von NAB 365 (Clenbuterol)

The findings of acute, subacute and chronic toxicity studies in rats and dogs with the new beta-mimetic agent 4-amino-alpha-[(tert.-butylamino)methyl]-3,5-dichlorobenzyl alcoholhydrochloride (NAB 365, clenbuterol) are reported. The longest period of investigation, with daily oral administration of the substance, was 18 months (rats) and 12 months (dogs). No abnormalities of any kind were found in the rat studies which could be attributed to the substance. The administration of clenbuterol to dogs produced microscopically small lesions in the myocardium which were not dose-dependent and which were localised entirely in the papillary muscle of the left ventricle. The reason for these lesions was that dogs react to the substance with severe tachycardia, as a consequence of a reduction in diastolic blood pressure produced even by very low oral doses. Oxygen deficiency occurs which affects particularly the papillary muscle. The response to hypoxia is better capillarisation. This causes an improvement in the oxygen supply, which in turn prevents the spread of existing necroses and the development of further lesions.