Characterization of a slow-growing, transplantable rat mammary tumor (MCR-83): a model for endocrine-related cell kinetic studies.

Out of 24 primary mammary tumors, arising in rats of the WAG/Rij Wistar strain after low dose irradiation, with or without prolonged treatment with estrogen, a slow-growing, well differentiated adenocarcinoma (MCR-83) was selected. This tumor, induced by radiation alone, is independent of estrogen pellets for growth after transplantation into adult female rats, but nontransplantable into males or ovariectomized females. Measurements of tumor growth and contents of both estrogen and progesterone receptors on three successive passages are not indicative of a rapid progression in growth rate or to hormone independency. Ovariectomy and treatment with tamoxifen give a pronounced inhibition of tumor growth, whereas neither methotrexate nor cyclophosphamide is effective. Growth rate is significantly increased when rats are given 17 beta-estradiol. Flow cytometric DNA analysis as well as in situ S-phase cell detection with anti-bromodeoxyuridine antibodies show a 3-fold increase in S-phase fraction cells within 4 days after the onset of estrogen treatment. No spontaneous metastases have been found so far, but lung nodules develop after i.v. inoculation of tumor cells. From one of these nodules a fast-growing, hormone independent subline (MCR-86) has been derived, showing both lymphatic and hematogenous dissemination upon s.c. transplantation. By showing several features of hormone responsive human disease in its early stage of progression the MCR-83 tumor system may be a clinically relevant model for studies on endocrine regulation of tumor growth and its therapeutic manipulation.

The effects of Goldblatt hypertension on development of the glomerular lesions of diabetes mellitus in the rat.

Rats with classic Goldblatt (two-kidney) hypertension had diabetes induced by streptozotocin. After four months of diabetes, glomeruli of the unclipped kidney of hypertensive diabetic rats had markedly increased diabetic changes, including mesangial matrix thickening and mesangial immunoglobulin (IgG and IgM) and complement (C3) localization, when compared with glomeruli of the contralateral-clipped kidneys. Further, glomeruli of the unclipped kidneys of hypertensive diabetic animals had more mesangial thickening and IgG and IgM staining than glomeruli of normotensive diabetic rats. Although glomeruli of clipped kidneys in hypertensive diabetic rats had less mesangial thickening than glomeruli of normotensive diabetic rats, this did not reach statistical significance. However, these glomeruli did have significantly less IgG, IgM, and C3 staining compared with glomeruli of normotensive diabetic animals. Mesangial thickness in glomeruli of clipped and unclipped nondiabetic hypertensive rats did not differ from that in normal animals. However, there was less mesangial IgG staining in clipped than in unclipped kidneys of nondiabetic hypertensive rats or in kidneys of normal animals. We have interpreted these results to imply that alterations in nephron hemodynamics combine with the diabetic state to influence the rate of development of diabetic glomerulopathy in rats.

Experimentally induced pemphigus vulgaris in neonatal BALB/c mice: a time-course study of clinical, immunologic, ultrastructural, and cytochemical changes.

Pemphigus vulgaris autoantibodies (PV IgG) promote cell detachment in epidermal cell cultures and acantholysis in the epidermis of neonatal BALB/c mice in vivo. We have studied the evolution of the immunologic and ultrastructural changes in the epidermis of BALB/c mice that receive parenteral injections of PV IgG. Neonatal BALB/c mice received a single i.p. injection of PV IgG (10 mg/g body weight) or control IgG from normal humans. The skin and serum of these animals was obtained at 0, 1, 3, 6, 12, 18, and 24 h post injection, and examined by immunofluorescence (IF), electron microscopy (EM), and immunoelectron microscopy (IEM). PV IgG was detected in the mouse serum and bound to the epidermal cells as soon as 1 h after injection by IF and IEM. The intensity of the binding in the skin (by IF) increased sharply between 3 and 6 h, and remained positive at 24 h. Early epidermal cell detachment was demonstrable by EM at 1 h as widening of the epidermal intercellular spaces (ICS), and by 6 h the ICS between desmosomes had detached completely. Desmosomal junctions are the last to separate, occurring at 12-18 h. At this point, complete cell detachment occurred in the suprabasilar layers of the epidermis. Basal cells remain attached to the underlying dermis (tombstone row). Coincident with cell detachment, intracellular tonofilaments retracted from the cell periphery and clustered in a perinuclear position. IEM confirmed the binding of PV antibodies to the surface of epidermal cells in early and established lesions. This study demonstrates that the early immunologic and ultrastructural changes that occur in human pemphigus vulgaris are reproduced in this mouse model of the disease.

An immune-mediated guinea pig model for lower motor neuron disease.

Guinea pigs were immunized with motor neurons from swine spinal cords. One month after the last of five serial immunizations, the recipients showed progressive weight loss. By seven months of age, five of the six immunized animals had died. Pathological examination showed destruction of motor neurons in the spinal cords without demyelination, but with atrophy of the related skeletal muscle groups. By immunofluorescent and histochemical tests, serum from the guinea pigs was shown to react with motor neurons of swine and guinea pig cord. This experimental disorder of guinea pigs appeared to be based on the immunologically mediated destruction of motor neurons and it may serve as a model for the human motor neuron diseases.

Mandibulofacial dysostosis (Treacher Collins syndrome): a new proposal for its pathogenesis.

Acute exposure to 400 mg/kg 13-cis retinoic acid (13-cis RA, isotretinoin, Accutane) on the ninth day postfertilization in mice (a time that corresponds to the fourth week postfertilization in humans) results in malformations that characterize mandibulofacial dysostosis (MFD, Treacher Collins syndrome). Deficiencies in the infraorbital region and in the mandibular ramus and condyle, abnormalities of the secondary palate, and external ear malformations were observed. Light and scanning electron microscopic analyses of affected embryos illustrate that within 12 hours of maternal 13-cis RA treatment, markedly excessive (possibly premature) cell death occurs in regions where some of the cells are normally destined to undergo programmed cell death. Previous studies with retinoids have shown that they labilize lysosomal membranes and expand and strengthen regions of programmed cell death. Of particular interest for this study was cell death occurring in the dorsal (proximal) aspects of the maxillary and mandibular prominences of the first visceral arch, the second visceral arch, and the first visceral cleft, areas that correspond to the locations of the first and second arch ectodermal ("ganglionic") placodes and first closing membrane, respectively. The derivatives of this region are those that are severely affected in MFD. As described in previous reports from this laboratory, 13-cis RA is known to interfere with neural crest cells, resulting in major craniofacial malformations. However, the exposure times involved were earlier than those described herein. It is hypothesized that effects on the first and second arch ectodermal placodal cells at a time following the release from the neural folds of neural crest cells into the developing cranial region are of great significance in the pathogenesis of MFD. This is in contrast to the prevailing hypothesis that these malformations are the direct result of a primary interference with neural crest cells.

The surgical pathologist as researcher.

Most surgical pathologists have the opportunity to perform research. Research in surgical pathology can be classified as: (1) observational; (2) manipulative with human tissues; (3) experimental with nonhuman models; and (4) technical, instructional, and delivery. Examples of each of these forms of research are presented, as are comments on the academic stature and funding problems of research in surgical pathology.

Hemiparkinsonism in monkeys after unilateral internal carotid artery infusion of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP).

Infusion of MPTP (0.2-0.8 mg/kg) into the right internal carotid artery of monkeys produces toxin-induced injury to the right nigrostriatal pathway with sparing of other dopaminergic neurones on the infused side and with negligible or little injury to the opposite, untreated side. There are contralateral limb dystonic postures, rigidity, and bradykinesia, but the animals are able to eat and maintain health without drug treatment. Spontaneous motor activity is attended by circling towards the injured side, whereas treatment with L-DOPA/-carbidopa or apomorphine stimulates circling towards the intact side. Dopamine and dopamine metabolite levels are normal in the left caudate and putamen, but markedly depressed on the right (MPTP-treated) side. This animal hemiparkinsonian model will be useful in studies of volitional movement control, drug treatments of Parkinson's disease, and functional efficacy of brain tissue implants.

Can pseudomonas infection in experimental animals mimic Kawasaki's disease?

Experiments aimed at producing a model of Kawasaki's disease by injecting animals intraperitoneally with Pseudomonas bacilli are described. Injection of large numbers of bacilli into mice caused rapidly fatal sepsis. With appropriate numbers of organisms, some mice died within 3 days, most remained healthy, while in some an inapparent chronic disease developed. Positive blood cultures were occasionally obtained 4-17 weeks after the slow infection. An alcohol-precipitable polysaccharide, which could be measured by Roe's procedure for levan, was found in 20% of the experimentally infected mice. We suggest that this substance was partly responsible for the course of the infection. Severe vasculitis with little acute inflammatory reaction and carditis with coronary aneurysms were often obtained by injecting mice and guinea-pigs with supraliminal doses of bacilli at the same time as their immune system was impaired by treatment with either nitrogen-mustard or cyclophosphamide. We suggest that pseudomonas infection in immunologically deficient animals may mimic Kawasaki's disease and that a similar mechanism may operate in the natural form of the disease in children.

Experimental Toxoplasma retinitis: a light and electron microscopical study.

In a light and electron microscopical study of the morphological lesions of acute experimental Toxoplasma retinitis in the rabbit, produced by intravitreal inoculation with RH strain T gondii, all layers of the retina were found to be infected with the parasite. The Bruch membrane appeared to be a relatively impermeable barrier to invasion by the parasite. The underlying choroid showed an inflammatory cellular infiltrate but was free of organisms. Evidence of lateral spread of infection between the layers of the retinal tissue was observed. Examples of glial cell infection were also seen. Trophozoities may enter the brain by spreading along contiguous glial cell elements of the optic nerve; retinal tissue destruction occurs by direct invasion of cells by trophozoites. In other areas, tissue destruction by inflammatory cells occurred in the absence of organisms and may indicate an immunologically induced process of tissue destruction.

Lack of amyloidosis and renal disease in A strain mice.

Amyloid deposition in two sublines of the A strain mouse, a reputedly reliable murine model of spontaneous amyloidosis, was reevaluated using combined green polarization birefringence after Congo red staining and a fibrillar ultrastructure for amyloid identification. Both sublines were found to be devoid of amyloid at an age when the A strain mouse had been reported to have a high incidence of papillonephritis, amyloidosis, and death. This finding indicates a need for reassessment of this and other traditional models of spontaneous amyloidosis.

Possible origin of synovial lining cell hyperplasia in rheumatoid arthritis.

A perplexing feature of rheumatoid arthritis is the increase in the number of synovial lining cells with no mitotic activity. This feature has been investigated in the rabbit model. Rabbits with the established condition were injected into the affected joint with tritiated thymidine and killed either up to 24 hours later, or at 3 or 7 days. The location of labelled cells, detected by autoradiography, showed the label predominantly in the stroma in the former, and mainly in the lining cells in the latter, indicating that the lining cells were derived by recruitment from active cells deep in the stroma.

Genetic aspects of tumour metastasis.

The application of techniques for the transfer of genetic material between cells when used with recombinant DNA technologies and gene cloning procedures hold exciting possibilities for the genetic analysis of the metastatic behaviour of tumour cells. So far these genetic studies have produced confusing results, but some of the problems have been defined more clearly. For a more complete understanding of the metastatic phenotype a more critical analysis of the models used to mimic the process and a greater appreciation of the deficiencies in the techniques applied to study it are necessary.

[Experimental Junin virus infection in the mouse: rototype of the disease]. / Estudio de la infeccion experimental del ratón por virus Junin: enfermedad tipo

As previously postulated, the pathological changes which develop in 1-4 day old mice after intracerebral inoculation of 1-1000 DL50 of Junín virus prototype strain (XJ), was designated as experimental hemorrhagic fever of the mouse EHFm. In this paper, virus distribution, hematological alterations, interferon and circulating antibody responses are described. A mortality of 93.45% occurred between 9 and 20 days post-infection (p.i.), with 81.6% of death occurring between 11 and 18 days p.i. This last period can be considered to be the critical period of the disease. The study of virus distribution shows that the brain, where the virus was inoculated, was the only place where virus could be detected 48 hs, p.i. Four days p.i., the titer in the brain increased remarkably and virus was detected in the blood. Virus, within the same values, could be isolated up to the 10th. day. Invasion of liver and spleen occurred on the 10th. and 15th. days p.i., respectively (Fig. 1). The onset of clinical symptoms coincided with widespread disemination of the virus. CF antibodies were found only 15 days p.i., with a titer of 1/64. Neutralizing antibodies remained below detection levels during the whole experiment (Fig. 1). Surviving mice (6.3%) had high circulating antibody titers 40 days p.i. This result would indicate that the morobidity of EHFm is aproximately 100% (Table 1). Poor interferon response was registered in all the organs examined, indicating a low intereron producing ability for Junin virus6. Total leukocytes and lymphocyte counts showed a slight tendecy to drop, although the values were within normal range during the first ten days (Table 2, Fig 1). On day 14 p.i., a statistically significant decrease (p less than 0.001) was found. This leuko-lymphopaenia continued until death of the animals. It is expected that the data presente here would contribute to a better understanding of the Junin virus infection in the newborn mouse, the experimental animal used.

Etiology and pathogenesis of monophasic and relapsing inflammatory demyelination - human and experimental.

The close similarity of the CNS lesions in cr-EAE and MS renders this model especially valuable for the study of pathogenetic factors, leading to the formation of inflammatory demyelinated plaques. Recent evidence indicates, that various immune reactions, directed against different CNS antigens cooperate in the formation of the plaques. Furthermore it is discussed, that a combination of virus infection and autoimmunity may result in similarity structured lesions. It is thus propose that multiple different etiologic factors (autoimmune as well as exogenous events) may lead to the clinical pathohistological syndrome of multiple sclerosis.

Animal model of conjunctival primary acquired melanosis.

A condition clinically identical to human conjunctival primary acquired melanosis (PAM) was induced in 16 of 20 Dutch (pigmented) rabbits after weekly topical 60-microliters applications of a 1% solution of 7,12-dimethylbenz[a]anthracene (DMBA) in acetone. Pigment stippling appeared in the conjunctiva as early as 5 weeks after the initial carcinogen application. Confluent patches of flat pigmentation appeared over the palpebral conjunctiva 18 weeks after the onset of treatment and showed progressive lateral enlargement and darkening. Histologically, a spectrum of changes from increased melanin production and melanocytic hyperplasia without atypia (resembling the human condition of PAM without atypia) through atypical melanocytic hyperplasia (resembling human PAM with atypia) was identified. The development of this model permits further investigations to explore and explain the clinically observed phenomenon of waxing and waning of PAM and its promotion to conjunctival malignant melanoma.

Cerebral hemiatrophy--correlation of human with animal experimental data.

We report the neuropathologic findings in a 63-year-old white male with a history of birth asphyxia, cerebral palsy, seizures and mild mental retardation in conjunction with similar brain pathologic findings in animal models of perinatal asphyxia. The human case showed a left cerebral hemispheric hemiatrophy associated with an extensive ulegyria involving all cerebral lobes on that side and a single microscopic focus of cortical atrophy in the right hemisphere. Among a large number of experimental perinatal asphyctic exposures only an occasional animal, like the human case described, showed unilateral hemispheric injury with softening and necrosis if examined early and ulegyria with hemispheric hemiatrophy if examined late. The present paper suggests that perinatal asphyxia under specific pathophysiologic conditions may cause unilateral brain injury. Our experimental studies suggest the specific condition of perinatal asphyxia potentially causing unilateral or asymmetrical brain damage is marked hypoxemia combined with substantial reductions in blood pressure but without circulatory collapse. Given these conditions, the asymmetry of the brain damage likely reflects fetal head position within the gravitational field relative to the heart. With disturbed cerebral blood flow autoregulation from asphyxia, the gravitational field likely accentuates the ischemia of those brain areas most elevated above the level of the heart. Thus, we postulate head position may play a pivotal role in defining brain regions that are damaged in hypotensive perinatal asphyxia. This interpretation may affect the intensive care of hypoxemic, hypotensive newborns aimed at minimizing the risk of brain damage.