Preclinical safety testing of species-specific proteins produced with recombinant DNA-techniques. An attempt to transfer current experience into future testing strategies.

Preclinical toxicity studies in animals with species-specific recombinant DNA products have now been performed for several years. An interim statement on the significance of these animal tests and their ability to predict adverse effects in humans therefore appears indicated, with the aim of deducing future testing strategies. The experience accumulated so far shows that the animal models have failed to predict adverse effects subsequently observed in man. Immunogenicity of these proteins further restricted the usefulness of standard toxicity tests. There is also increasing evidence that animal tests on the toxic potential of impurities contained in the products are markedly inferior in sensitivity to analytical and quality control methods. Thus, modified testing programs are proposed to demonstrate safety rather than target organ toxicity using rodents and small non-rodent species and restricted dosing; furthermore the study duration should be limited by the detection of immunogenic responses.

Ultrastructural and histochemical aspects of prostatic secretion in dog.

The reaction of canine prostatic epithelium was studied ultrastructurally and histochemically (acid phosphatase, zinc) in mature Beagle-dogs 15 minutes after intravenous application of pilocarpine (1 mg/kg body weight). In the normal prostate we found only merocrine secretion with exocytosis of secretory granules. Exocytosis persisted after stimulation with pilocarpine, but was quantitatively greatly increased. Apocrine or holocrine types of secretion were neither found under resting conditions nor under extreme functional stress of the glandular epithelium. Histochemically a distinct decrease of the activity of acid phosphatase and of zinc in the apical part of the epithelium has developed, which corresponds to the ultrastructurally obvious loss of secretory granules.

Peliosis of the female adrenal cortex of the aging rat.

Foci of apparent peliosis are regularly observed in the mid-zone of the adrenal cortex in female rats older than 600 days. The changes present range from ectasis of the sinusoids to extensive cystic change of the whole organ. This lesion occurs almost exclusively in female animals and was seen in only one of 50 male animals older than 600 days examined. Experimental stimulation or inhibition did not influence adrenal peliosis. Electron microscopically, there was marked pericapillary edema with collapse of the capillaries, and erythrocytes and thrombocytes were seen infiltrating the edema. Fibrin accumulated in the larger foci. Degenerative alterations were not observed either in the epithelial cells of the cortex or in mesenchymal cells. The pathogenesis is unknown, but the possible role of constant estrus in aging female rats will be discussed.

Pathology of prostatic cancer.

From 1972 to 1975, 6758 clinical prostatic carcinomas were recorded at the prostatic carcinoma registry in Homburg/Saar. 52% of the patients are between the age of 65 and 75, 22% younger than 65. We distinguish between 4 basic types: the highly and poorly differentiated adenocarcinomas, the cribriform and solid anaplastic carcinomas. 46% of the carcinomas are of uniform architecture, 54% are pluriform differentiated whereby very often the cribriform carcinoma is present. 82% of all the cases and over 70% of the carcinomas in men under the age of 55 can be allotted to the stages B to D according to FLOCKS. All histologic patterns are found in young as well as in old men. Fastly proliferating and poorly differentiated prostatic carcinomas are predominant. Contrary to these features there are in stage 0 and the latent carcinoma highly differentiated adenocarcinomas in 41.8%, e.g. 57% with obviously low malignancy. They remain symptom-free so that they are only discovered incidentally during lifetime or during autopsy. The incidental carcinoma represents only 7% of the biopsy volume, the latent carcinoma 36.4% in men after the age of 45. Its frequency, the number of tumour foci and extension in the prostate increase with progressing age. The course of the clinical prostatic carcinoma under therapy can be controlled via biopsy. Thus, it is possible to discover in about 20% of the cases primarily therapy-resistant tumours. Other tumours show a complete regression and aside we find tumours with temporary regression and further tumour progression. Primarily resistant to conservative treatment are the transitional cell carcinomas of the prostate which, therefore, have to be differentiated from the solid prostatic carcinomas.

Chemodectoma of the larynx. A clinico-pathological study.

The present case report is concerned with a clinico-pathological study, including ultrastructural investigation, of a rare and uncommon laryngeal tumour, a chemodectoma, in a 62 year old patient. There have been 23 cases of laryngeal chemodectomas reported in the literature, and only three of them, including our own report, were investigated by electron microscopy. The tumours arise from the superior and inferior larynegeal nonchromaffin paraganglia or possibly from Kultschitzky-cells of the normal bronchial mucosa. Ultrastructurally they have all the characteristics of apudomas whose parent cells (APUD-cells), usually show endocrine function and probably have their origin in the neural crest. The tumours show an aggressive type of behaviour, despite usually benign histological features when compared to chemodectomas at other sites in the head and neck region. Surgery is thus the therapy of choice.

[Ultrastructural and enzyme-histochemical alterations of the dog prostate following castration (author's transl)]. / Ultrastrukturelle und enzymhistochemische Veränderungen der Hundeprostata nach Kastration.

Orchiectomy leads to morphologic and functional alterations of the prostate in dogs within 120 days. The glandular epithelium of the acini under the light microscope shows an advanced atrophy with some remaining slit-like lumina. Ultrastructurally, castration results in loss of cell polarity with preserved epithelial compounds. The columnar epithelium is transformed into small polygonal cells with regressive alterations of nucleus, rough endoplasmatic reticulum, mitochondria and Golgi apparatus. These cells show depositions of lipoids and glycogen. Functionally, gonadectomy results in a loss of secretory activity correspondingly secretory granules that are normally present in large numbers are conspicuously absent, the reduction of rough endoplasmatic reticulum and Golgi apparatus too are expressions of the cessation of synthesis of secretion. This is also indicated by the activity of acid phosphatase that is barely demonstrable in the apical portion of the cytoplasm of atrophic glandular epithelium following castration. Only insignificant changes on the other hand are found in the activity of alkaline phosphatase following withdrawal of androgens, this enzyme does not mirror the atrophy due to castration.

Ultrastructural and enzyme-histochemical studies of the prostate of the dog under the effect of estradiol.

The prostate of 4 mature pure bred Beagles 12 months old was studied 3 weeks following a single i.m. injection of 1 mg estradiol/kg body weight by means of histochemistry (acid and alcaline phosphatase) and electron microscopy. Four 11 months old Beagles served as controls. Estradiol leads to a variable reaction of glandular epithelium. There is an atrophy of active secretory cells, probably due to an inhibition of the release of ICSH by the anterior pituitary lobe, that in turn leads to a deficiency of androgens. The residual secretory function is not sufficient for normal synthesis of secretory granules, recognizable through the decrease in electron density of secretory granules and the extensive loss of activity of acid phosphatase. Under physiologic conditions it corresponds in its localization to the amount of secretory granules lying in the apical portion of the cytoplasm. The basal reserve cells show an ambivalence. Normally under the predominant influence of androgen they do not show any metaplasia, but they differentiate into the secretorely active epithelial cell. Without stimulation by androgens, estradiol leads to a basal cell proliferation with squamous metaplasia particularly in the dorso-lateral lobes close to the urethra. The activity of alcaline phosphatase shows a minor decrease in the capillary endothelium under estradiol. With increasing maturation of the metaplastic squamous epithelium the activity of alcaline phosphatase increases in the upper cell layer.