Changes in the aging rat retina

To characterize aging as a factor responsible for structural changes, the retinae of 47 Wistar-derived albino rats and 50 pigmented rats of the Norway and BDE (Han) strains between the ages of 1 and 36 months were examined by light and electron microscopy and analyzed for changes in cell densities. In all 3 rats strains there was an overall decline in nuclear densities of outer layer nuclei by 38-50% and inner layer nuclei by 27-33% between the ages of 1 and 27 months. Over the same age range, the ganglion cell loss was comparable to the decline in the inner nuclear layer. Neuronal cell death occurred at all ages and was more pronounced in albino rats. Moreover, in albino rats, cones were more resistant than rods to destruction by age and ambient light. As age-related ultrastructural changes in the retinal pigment epithelium (RPE) (1) a substantial accumulation of lipofuscin; (2) an apparent thickening of the basement membrane; (3) greatly enlarged and pleomorphic basal infoldings, and (4) shorter apical microvilli were encountered. Besides mature stage IV melanosomes 27-month-old BDE (Han) and 36-month-old Norway rats also revealed stage III melanosomes. Tyrosinase activity in peripheral RPE cells could be demonstrated in Norway rats up to 12 months old and BDE (Han) rats up to 24 months old. Characteristics of RPE cells in old rats of these two pigmented strains were also melanolysosomes, melanophagolysosomes and melanolipofuscin granules. Age-related changes in retinal vessels were found in the superficial and deep capillary network and consisted of a 2- to 3-fold increase in thickness of the capillary basement membrane.

Calcified foci at the junction between adrenal cortex and medulla of rhesus monkeys

The occurrence of calcified foci at the junction of adrenal medulla and cortex in monkeys obtained from toxicity studies during a 10-year period is reported. The survey included reinvestigated adrenal samples from 274 male and 270 female rhesus monkeys and 52 male and 52 female cynomolgus monkeys. The incidence of calcified foci was 46% in male and 45% in female rhesus monkeys, and 6% in male cynomolgus monkeys, while their females did not show the lesion. In male rhesus monkeys, the mean number of foci was 4 for both glands, in females, 2 for the right and 4 for the left one. Initial stages indicated that the lesions develop possibly from focal apoptosis of medulla cells followed by a dystrophic mineralization. No correlation was observed concerning dose groups, test article, study length, testing facility, origin of monkeys, their sex, age, diet or final body weight. The foci of mineralization were dystrophic, species-specific in the rhesus monkey and possibly related to stress. The location of the foci at the cortico-medullary junction, precisely the location of the remnants of the fetal zone, may indicate their origin from this zone.

Long distance image transfer: first results of its use in histopathological diagnosis

Histopathological images were transferred by use of normal telephone lines between three pathology institutes located in three different cities in the FRG. Images were digitized using a colour TV camera and stored in a special computerized image transmission system. The stored image was transferred and visualized on a (receiver) colour TV screen after dialing the telephone number connected to the receiver image transmission system. An additional telephone dialogue was activated by use of a normal acoustic telephone, and the diagnostic difficulties of the underlying image were discussed. Diagnostic assistance was possible in all transferred cases as well as histopathological diagnosis. Resolution of the images was set at 512 x 512 pixel x 8 bit. Image transfer time was 3.2 min on average. The differences between the original and transferred image were measured by "retransfer" of the original image and by subtracting the two images from each other. No major transfer errors could be measured.

A contribution to indirect ophthalmotonometry in beagles

A test of suitability of the electroimpression tonometer from Fritz Schwarzer GmbH, Munich, for measuring intraocular pressure in dogs was performed. Intraocular pressure of 63 clinically healthy English beagles was measured in both eyes using the instrument with different plunger weights. Intraocular pressure and volume of corneal depression during measurement were determined as a function of the plunger weight from readings on the tonometer with the aid of Friedenwald's tables (2). Using Friedenwald's law and with knowledge of the rigidity coefficient, an intraocular pressure of 32.7 mmHg was found, with individual variations between 12.8 and 54.2 mmHg. The rigidity coefficient for dogs, which was determined by linear regression, was, on average, 0.0103. Differences between male and female dogs were not significant for either parameter. A conversion table for eyes with a rigidity factor of 0.0103 is attached. Intraocular pressure as a function of plunger weight and the reading of measurement is shown in mmHg. In our measurements the Schwarzer electrotonometer for determination of intraocular pressure provided easily reproducible readings.

Benign melanoma of the choroid in a beagle: ophthalmological, light and electron microscopical investigations

A pigmented choroidal tumor was diagnosed in a 13-month-old male beagle. The tumor was observed ophthalmoscopically over a period of seven years. Light and electron microscopical features are those of a benign melanocytic tumor with marked histological similarities to uveal nevus in man.

[Operation on a congenital cataract in a Siberian Tiger]

A cataract operation in a young Siberian tiger is reported. This 5-month-old tiger, presenting with blindness, showed bilateral residual pupillary membranes and anterior polar cataracts combined with nuclear cataracts. After unilateral intracapsular extraction of the lens, the tiger adapted well to the improvement in sight and behaved almost like an animal with normal vision. The animal died 3 months post-operatively from unknown cause. Histological examination of the aphakic eye showed, at the site of operation on the cornea, an intact epithelium with discrete infiltration of the stroma together with low-grade vascularisation. In the eye not treated operatively, both an anterior polar cataract with adherent pupillary membrane strands and a central cataract were seen. Of particular note, when comparing this large wild cat with the domestic cat, was the marked development of the tapetum lucidum (up to 30 cell layers).

Fixation-induced cyst-like spaced in the brains of rabbit foetuses

During teratologic trials, routine investigations of 4261 brains from rabbit foetuses, fixed in Bouin's solution and sectioned by Wilson's free-hand razor blade technique, revealed cyst-like spaces in the brains of 164 foetuses (3.8%). The cyst-like spaces, characterised by the absence of an epithelial or endothelial lining, were usually solitary and occurred mainly in the massa intermedia of the thalamus. The spaces were found almost as ofter in control foetuses as in those from treated animals. On the basis of histologic examination and different fixation techniques, involving a further 1430 foetuses, these cyst-like spaces, previously interpreted as strain specific brain malformations, can be regarded as fixation artefacts.

Carcinogenicity study of lindane in the mouse

Linadane (gamma-BHC) was investigated for its possible carcinogenic effect on 500 mice (250 males, 250 females) of the Chbi: NMRI (SPF) strain in a study lasting 80 weeks. A substance-related production of tumours was not evident at the dosage levels employed (12.5, 25 and 50 ppm). The tumours found corresponded in type and frequency to those occurring spontaneously in this strain. Electron-microscopical examination of livers, carried our at the same time, provided no evidence of Lindane-induced fine structural hepatocellular alterations.

Aberrant nerve fibre bundles in the retina of the dog

Systematic ophthalmoscopic examinations of 2511 Beagles, test animals in 72 long-term toxicological studies, showed archiform thin white stripes in the fundi of 98 animals (3.9%). The stripes occurred in one or both eyes in the non-tapetal fundus of the two lower quadrants. Examinations of the fundus of some dogs by fluorescence angiography and ophthalmoscopy with red-free light showed that these fibriform stripes were in the retina. Histological examination showed these stripes to be nerve fibre bundles (5-120 axons) lying at the ganglion cell layer. The ultrastructure of the fibres did not differ from that of the nonmyelinated neurites of the fibre layer. The stripes may be retinal nerve fibres with a normal structure but could be distinguished from fibres of the nerve fibre layer by their intraretinal location and by their course.

A contribution to the question of the possible hepatocarcinogenic effects of lindane

The possible hepatocarcinogenic effect of lindane was studied in an 80-week study using 500 NMRI mice (strain Chbi : NMRI (SPF)). After giving doses of 12.5, 25 and 50 ppm in the food no compound-induced liver tumours were observed. Neither the occurrence of lymphatic leukemia, malignant haemangioendotheliomas, reticulum cell neoplasms nor liver cell adenomas could be related to the administration of the compound. In view of the actual residue level of lindane the probability of carcinogenic risk to man would appear remote.

Pupillometric studies in the beagle dog

A method of measuring pupillary diameter in the dog using a Kowa RC-2 fundus camera, to which an eyepiece graticule had been fitted, is described. Pupil diameter was measured either directly by reading off from the calibrated graticule or from photographs. The pupillary diameters of 105 (53 male, 52 female) untreated English beagles aged between 8 and 32 months were measured under light intensities of 150-200 lux and 1000-1400 lux. Mydriatic and miotic pupillary diameters were measured in 62 male and 80 female dogs. Time-effect curves were plotted for two groups of 5 beagles receiving 75 mug/kg or 175 mug/kg atropine and 100 mug/kg or 300 mug/kg propantheline intravenously. The dose-effect curve for propantheline was found to be linear. A dose of 109 (97-121) mug/kg propantheline increased pupillary diameter by 3 mm, 20 min after administration. The time- and dose-effect curves, the significant sex differences and age dependency seen in this study indicate both a high degree of accuracy and the suitability of both of these methods for use in pharmacological and toxicological studies.