R. Hess

The optimization test in the guinea pig in relation to other predictive sensitization methods

The allergenicity of various compounds was tested by means of the optimization procedure in the guinea-pig. Results with antibiotics, preservatives, fragrance raw materials and miscellaneous contactants are reported. Their relevance is critically discussed in relation to other animal sensitization methods (Draize, Bühler, open epicutaneous and maximization tests). Predictive animal tests are compared with those used in human allergy (Shelanski & Shelanski; maximization test). The importance of animal methods entailing the use of adjuvants is underlined.

Comparative study of the teratogenicity of phenobarbitone, diphenlhydatoin and carbamazepine in mice

Three selected anticonvulsants, phenobarbitone (PHB), diphenylhydantoin (DPH) and carbamazepine (CAA) were examined for embryotoxic and teratogenic activity in albino mice. After oral treatment of the dams during the period of organogenesis (days 6-15 of gestation) with both PHB and DPH in doses causing marked symptoms and signs of toxicity (40 and 170 mg/kg/day respectively), an abnormally high incidence of cleft palate was observed in the foetuses (4.3% and 9.3% resp.). In a cumulative control group of foetuses, the incidence of this particular malformation was only 0.13%. No significant change in the malformation rate was seen after the administration of CAA in doses up to 250 mg/kg/day. Slight to moderate retardation of foetal growth was noted after treatment with DPH and CAA, but only at the higer and toxic dose levels. DPH also increased the incidence of early embryonic deaths (deciduomata).

Effects of cyclophosphamide on embryonic development in the rabbit.

Groups of pregnant rabbits were given cyclophasphamide (Endoxan Asta®) in single intravenous doses of 30 mg/kg on different days from the 6th day to the 14th day of gestation. On the 28th day (shortly before term) the foetuses were removed by caesarean section. Administration of cyclophosphamide about the time of implantation led to an increase in the number of early embryonic deaths. Injection of cyclophosphamide at the later stages resulted in an increased number of foetal deaths. About 10% of the foetuses from dams treated on the 7th day of pregnancy exhibited malformations, in particular disturbances of ventral closure. When cyclophosphamide was administered on the 11th day of pregnancy more than 30% of the foetuses were found to have median cleft palates and other malformations of jaws and lips. All the foetuses from dams treated on the 12th day showed oligodactylia and brachydactylia. The latter type of malformation was also present when treatment was given on the 13th day. The embryotoxic effect of cyclophosphamide administration was particularly evident in the early periods of embryonic development. In contrast, the teratogenic action was more confined to the later periods of organogenesis. Teratogenicity occurred in two peaks corresponding to characteristic ‘phaenocritical’ phases of development. The first and lower peak coincided with the period of histiotrophic nutrition and the second and higher peak corresponded to the heamotrophic phase. It is concluded that embryotoxicity and teratogenicity are largely independent phenomena.

Predictive evaluation in animals of the contact allergenic potential of medically important substances. II. Comparison of different methods of cutaneous sensitization with "weak" allergens.

Results of the optimization method and of other methods used to assess contact allergy in laboratory animals were compared with known epidemiological data on the occurrence of hypersensitivity reactions in man. Tests were performed with preservatives {formalin, ethylenediamine and sorbic acid), drugs (penicillin G, benzocaine and sulphathiazole) and other contactants belonging to widely different chemical classes (p‐phenylenediamine, triclosan, pyrazole derivatives, nickel and chrome salts, eugenol, isoeugenol and mercaptobenzothiazole). The degree of sensitization achieved in guinea pigs by the optimized procedure (intradermal test with adjuvant combination) and the maximization procedure was invariably superior to that produced by the epidermal method using prior irritation of the site of application. Both the optimized procedure and the maximization test seem to be capable of identifying contact allergens that cause hypersensitivity reactions in as few as t in 10,000 of the human population as a whole. The optimization test merits consideration as a standardized and efficiently predictive procedure.

The optimization test in the guinea-pig. A method for the predictive evaluation of the contact allergenicity of chemicals

Guinea-pigs were sensitized with various substances (DNCB, penicillin G, PPL, ethylaminobenzoate, formalin) by the Draize method, the maximization method and the new optimization method (intracutaneous test employing adjuvant). The advantages of the optimization method favouring its adoption as a standard sensitization test are discussed in the light of the results obtained by this method and with the two established tests.

Clioquinol and 2,5-hexanedione induce different types of distal axonopathy in the dog.

SummaryThe central distal axonopathy induced in dogs by the administration of high doses of clioquinol is contrasted with the central-peripheral distal axonopathy precipitated by intoxication with 2,5-hexanedione. Mature, pure-bred Beagle dogs received a daily oral dose of 400 mg/kg of clioquinol for up to 7 months, or 1 ml per animal (approximately corresponding to 110 mg/kg) of 2,5-hexanedione for up to 5 months. Intoxicated and control animals were killed and perfused at monthly intervals, so that the spatial-temporal development of the lesion could be followed and correlated with clinical symptoms. During the treatment, dogs intoxicated with 2,5-hexanedione developed symptoms of peripheral neuropathy consisting of flaccid weakness, muscle atrophy, hind-limb foot-drop and areflexia. By contrast, the dogs surviving clioquinol intoxication exhibited a stiff-legged gait, hyperreflexia but no muscle atrophy.Light and electron microscope examination of central and peripheral nervous tissue from dogs intoxicated with 2,5-hexanedione revealed giant axonal swelling and distal axonal degeneration. By contrast, dogs receiving clioquinol showed a distal axonal degeneration confined to the optic tract and the long spinal cord tracts, without any visible involvement of peripheral nerves.

Radicular Myelinopathy in Aging Rats

Naturally occurring degenerative lesions of nerve fibers in the spinal cord, spinal roots and peripheral nerves in nine male rats 877 days old were swollen myelin sheaths, forming “myelin bubbles.” The myelin swellings were distributed throughout the spinal tracts and the peripheral nerves, but most frequently in the lumbar ventral spinal roots. Although most axons surrounded by swollen myelin were intact, some were constricted and degenerated, while others showed signs of remyelination.

Predictive animal testing for photocontact allergenicity

The purpose of this investigation was to establish a standardized animal model to predict the photoallergenic potential of new chemical compounds. In a first series of experiments the main factors influencing the induction of photoallergenicity were evaluated (induction concentration, pH of the test solution, pretreatment of the irradiation site with sodium lauryl sulphate, additional use of adjuvant injections and routes of administration). Osram Ultravitalux lamps were utilized for these studies.

Differential susceptibility of peripheral nerves of the hen to triorthocresyl phosphate and to trauma

The nerve fibres of largest diameter and of greatest length are considered to be the most vulnerable to triorthocresyl phosphate (TOCP). In this study, the differential vulnerability of the particular sciatic nerve branches was determined in the course of TOCP neuropathy and of Wallerian degeneration. The branch innervating the lateral gastrocnemius muscle, made up predominantly of large-diameter fibres, proved most susceptible to TOCP. By contrast, after proximal sciatic-nerve transection, degeneration commenced in the lateral nerve of the third digit, containing long nerve fibres of small diameter.

Embryolethality in the mouse following treatment of males with cyclophosphamide at specific germ cell stages.

Male mice (NMRI strain) were given a single intravenous dose of 100 mg/kg cyclophosphamide. At various intervals corresponding to defined periods of spermatogenesis, they were mated with untreated females. A significant increase in the ratio of embryonic deaths was found when postmeiotic stages of spermatogenesis (i.e. spermatids and spermatozoa) had been affected, and this first occurred on day 3, when spermatozoa were already formed. Following disturbance of premeiotic stages of germ cell proliferation, a decrease in the number of successfully mated females or in the number of implantations of embryos indicated a reduction in fertility rather than a mutation event. There was no correlation between dominat lethal effects of cyclophosphamide and the results of cytogenetic investigations of the germinal epithelium.