Foreign-body tumorigenesis by vinyl chloride vinyl acetate copolymer: no evidence for chemical cocarcinogenesis.

We investigated whether vinyl chloride monomers, released from implants of vinyl chloride vinyl acetate copolymer (VCA), exerted cocarcinogenic activity and added thereby to the mechanism of foreign-body (FB) tumorigenesis. CBA/H and CBA/H-T6 mice were used. No evidence was found to indicate that chemical carcinogenic activity partakes in tumorigenesis by VCA implants. Hence it was concluded that VCA plastic is not suitable for the study of the combined process of FB/chemical cocarcinogenesis. Furthermore, experimental results obtained with VCA film implants were representative of FB tumorigenesis in the absence of demonstrable chemical carcinogenic activity.

Carcinogenesis from polymer implants: new aspects from chromosomal and transplantation studies during premalignancy.

Inbred CBA/H and CBA/H-T6 mice received implants of 15 X 22 mm plastic films. Plastic inserts and tissue capsules were cut in thirds at half monthly and monthly intervals. The first portion of the inserts and capsules was left in the original animal. The second portion was separated and individually transplanted into recipients that differed from the original animals with respect to the T6 marker chromosome. The third portion and all tumors which developed in original and recipient animals were examined by karyological, histological, and cultural methods. Film pieces caused tumors in recipient animals up to 9 months after transfer, capsule tissue only up to about 1 month after transfer. Tumors in original and corresponding recipient animals were identical in their chromosomal stemlines and pace of premalignant maturation. The karyotype of the stemline was never discovered among the film-attached cell population because there seemed to be no cell division. This points to the existence of a single, specific premalignant cell clone residing on the film surface in a dormant state of nondivision many months before tumor appearance. At the end, the (pre)malignant cells detached from the film, invaded the capsule tissue, and propagated to produce the tumor within about 4 weeks. The existence of a specific inhibition phenomenon during the premalignant phase is suggested.

Immunosuppression studies in foreign body tumorigenesis: no evidence for tumor-specific antigenicity.

Sarcomas were induced in CBA/H mice by sc implantation of 15 X 22 X 0.2-mm polyvinyl chloride vinyl acetate copolymer films. The animals were immunosuppressed with azathoprine, antilymphocyte globulin, or thymectomy. Sarcoma development was not accelerated in comparison to nonimmunosuppressed demonstrated in sarcomas of immunosuppressed mice. It was concluded that foreign body tumorigenesis in mice in neither associated with nor dependent on the emergence of tumor-specific transplantation antigens.

Foreign-body tumors of mice: strain and sex differences in latency and incidence.

Sarcomas were induced by sc implantation of unplasticized polyvinylchloride acetate films in female and male mice of strains AKR/J, BALB/cJ, BALB/cWat, CBA/H and CBA/H-T6, C3H/HeJ, C57BL/10ScSn, C57BL/6J-bgj, C57BL/cdJ, DBA/-1J l/LnJ, LP/J, SJL/J, X/Gf, 129/J, and hybrids (CBA/H-T6 X AKR/J)F1, (C57BL/10ScSn x CBA/H or CBA/H-T6)F1, (C57BL/6J-bgj x C57BL/6J)F1. The strains and sexes showed marked differences in incidence and mean latency of resulting tumors. Crucial information was provided for the selection of appropriate mouse strains for the study of interrelationships between genotypes, defined somatic properties, and the multifactorial process of foreign-body tumorigenesis.

Foreign-body tumorigenesis: in vitro isolation and expansion of preneoplastic clonal cell populations.

Foreign-body reactions were induced in coisogenic CBA/H and CBA/H-T6 mice by sc implantation of 15 times 22 times 0.2-mm unplasticized vinyl chloride vinyl acetate copolymer films. At 6 months' post implantation, implants and unopened tissue capsules were transferred to recipient animals of the T6-different partner strain. After another 3 months, part of the film/capsule complex was transferred to (C57BL/10ScSn times CBA/H-T6)F1 mice for tumor development. Capsule-derived and film-attached cells of the other part were separately cultured. Cultures consisting initially of euploid cells were often gradually replaced by different cells with specific aneuploid karyotypes which were identical with, or closely related to, those of the corresponding tumors. The cultured cells implanted in hybrid recipients at different passage numbers frequently gave rise to homologous tumors. Hence, it was possible to prepare in vitro cells with prefixed specific tumor determinants at different stages of preneoplastic maturation.

Foreign-body tumorigenesis: number, distribution, and cell density of preneoplastic clones.

Double 15 times 22-mm plastic films (two films on top of each other) were implanted subcutaneously in CBA/H-T6 mice. After 7.5, 8.5, and 9.5 months the films were removed. Each interior film (next to the abdominal wall), covered by a cell monolayer on one side only, was cut in four 7 times 10-mm segments. Wiping to 5 times 7, 4 times 4, 3 times 3, or 2 times 2 mm reduced the cell areas on three of them. They were then transferred to (CBA/H times CBA/Br)F1 or (CBA/H-Ty times CBA/Br)F1 recipient mice. Tumors arising from transferred film segments were analyzed as to chromosome number and morphology, sarcoma type, degree of anaplasticity, and posttransfer latency. We used these criteria to determine whether tumors originated from the same or different clones. From this information it was estimated that preneoplastic clones were present in limited numbers and that they were either widely disseminated or spatially restricted on the implant surfaces. The extent of clone dissemination appeared to be related to preneoplastic progression.

Foreign-body tumorigenesis induced by glass and smooth and rough plastic. Comparative study of preneoplastic events.

Foreign-body (FB) tumorigenesis was induced in female CBH/H and CBA/H-T6 mice and their hybrids by sc implantation of about 0.2-mm thick, large (660-720 mm2) or small (210-400 mm2) pieces of glass, smooth-surfaced plastic, or roughened plastic (rigid unplasticized vinyl chloride vinyl acetate copolymer). The tumorigenic process was analyzed in the various implantation groups by the evaluation of tumor incidences and latencies, and by the determination of 1) frequency of originator ("parent") cells, 2) appearance of preneoplastic cells in FB-reactive capsule tissue, 3) expansion of preneoplastic cell clones throughout the tissue capsule, and 4) pace of cellular preneoplastic maturation in terms of time remaining until neoplastic autonomy. Established methods included transfer of preneoplastic FB-reactive tissue capsules to recipient animals (hybrids of CBA/H and CBA/Br or C57BL/10ScSn). Specific preneoplastic events or stages of FB tumorigenesis were affected differently, depending on the size, material, and surface properties of implants.

Foreign-body tumorigenesis in mice: DNA synthesis in surface-attached cells during preneoplasia.

(CBA/H X CBA/H-T6)F1 mice were given sc implants of unplasticized vinyl chloride acetate 15 X 22-mm copolymer films. The animals were pulsed with [3H]thymidine at various times during the 15 months following implantation. DNA synthesis occurred in the film-attached cell population, predominantly macrophages, throughout the preneoplastic phase in both females and males. Giant cells with fewer than 10 nuclei were labeled synchronously and asynchronously. No DNA synthesis was detected in giant cells with more than 10 nuclei. Previous studies have shown that phagocytic inactivity and ultrastructural signs of functional dormancy are characteristic for the foreign-body-reactive macrophage. However, this investigation demonstrated that the macrophage was not dormant with respect to DNA synthesis.

Multiphasic incidence of foreign body-induced sarcomas.

Single or multiple plastic films (unplasticized vinyl chloride vinyl acetate copolymer) of different sizes and shapes were implanted s.c. in female CBA/H and CBA/H-T6 mice. Tumor incidence increased and accelerated with increased total surface area of multiple implants or with increased size of single implants. Tumor distribution curves over time were generally multiphasic. The profiles changed in proportionate relation to implant size. These findings indicate class differences between tumors according to latency. Since latency is known to be a predetermining characteristic of foreign body-induced tumors, class differences seem to exist at the originator cell level, reflecting diversity of intrinsic carcinogenic factors.

Etiological factors, stages, and the role of the foreign body in foreign body tumorigenesis: a review.

Attempts were made to analyze the process of foreign body (FB) tumorigenesis and to identify etiologically significant factors by correlating information in the literature and recent experimental data from our labroatory. It appears that the process of FB tumorigenesis is dependent on sequence of specific conditions as expressed by the following criteria: (a) cellular proliferation and tissue infiltration during acute FB reaction; (b) fibrosis of the tissue capsule surrounding the FB; (c) quiescence of the tissue reaction, i. e., dormancy and phagocytic inactivity of FB-attached macrophages; and (d) availability of a FB surface for direct contact with clonal preneoplastic cells. There is no indication that the initial acquisition of neoplastic potential and the determination of specific tumor characteristics are based on direct physical or chemical reaction between cells and the FB. These etiological key events occur presumably in mesenchymal stem cells associated with the microvasculature no later than during the acute stage of FB reaction and certainly long before clonal descendants of these cells are first found in contact with the FB surface. In fact, there is no reason to assume that cells with neoplastic determination may be present in normal tissue prior to the introduction of a FB and that the FB would only create the conditions required for stepwise preneoplastic maturation.

Cytogenetic analysis of leukaemic cells in the dog. A report of 10 cases and a review of the literature.

Cytogenetic abnormalities were found in 9 of 10 leukaemic dogs. Important findings were aneuploidy, especially hyperdiploidy, extra-metacentric chromosomes, double minute chromosomes and tetraploidy. Six dogs had a normal chromosome modal number of 78, but 4 other dogs had modal numbers of 54, 81, 83 or 85 and 156. One to 16 extra-metacentric chromosomes were seen in cells from 5 dogs. Double minute chromosomes, which appear to be markers for neoplasia, were seen in one or more cells from 3 leukaemic dogs. Too few adequate, simultaneous studies were available to compare cytogenetic results from blood and bone marrow samples of leukaemic dogs. Extra-metacentric chromosomes and double minute chromosomes were not found in cells from the normal control dogs and cells with more than 78 chromosomes were rare. Specific chromosome changes were not associated with any of the various types of leukaemia and prognosis could not be predicted from the cytogenetic findings but, in general, the prognosis was poor. However, it does appear that many or most dogs with leukaemia have chromosomal abnormalities. With additional research and improvements in leukaemia therapy, cytogenetic studies of canine leukaemia may provide diagnostic and prognostic information.

Cytogenetic analysis in nine leukaemic cats.

Eight of nine leukaemic cats had chromosomal abnormalities. The major differences between the healthy, FeLV-negative control cats and the leukaemic cats were the increased number of hyperdiploid cells and the presence of double minute or morphologically abnormal chromosomes in the leukaemic cats. Three leukaemic cats had cells with double minute chromosomes, while no normal cats had cells with double minute chromosomes. Tetrasomy or trisomy most frequently involved chromosomes C2 and B4. Monosomy was most common in chromosomes A3, C2, D4, E3 and F2. Chromosome abnormalities were also observed in bone marrow cells from two of three healthy, FeLV-positive cats and both cats with thymic lymphosarcoma. Increased numbers of hyperdiploid cells, double minute chromosomes and trisomy of C2 were the most important findings. No correlations between cytogenetic findings and diagnosis or prognosis were found. Additional research is necessary to determine the significance of chromosome aberrations in cells from healthy, FeLV-positive cats. If these changes prove to represent early neoplastic transformation, chromosome analysis could provide valuable diagnostic information and identify patients that might benefit from early chemotherapy. Results of this limited study indicate (1) chromosome aberrations are common in leukaemic cats, (2) chromosome changes are not completely random, (3) direct bone marrow technique for chromosome analysis is generally preferable in leukaemic cats and (4) the cat appears to be a good model in which to study chromosomal abnormalities in leukaemia, though more research is needed.

X trisomy in an Airedale bitch with ovarian dysplasia and primary anestrus.

A 79,XXX chromosome complement was detected in a four-year-old Airedale Terrier bitch examined for primary anestrus. Serum concentrations of luteinizing hormone (LH) and follicle stimulating hormone (FSH) were markedly elevated. Ovaries contained solid epithelial cords and large masses of interstitial cells but lacked follicles and corpora lutea. Somatic abnormalities were not observed. X trisomy is reviewed in six species in which it has been described.

A chromosomal reciprocal translocation (1q+; 14q-) in a boar siring reduced litter sizes.

In our initial cytogenetic surveillance of boars one of 15 was found to be hypoprolific. It averaged 7.1 piglets per litter in over 51 monospermic matings with sows which, with other boars averaged 10.8 piglets per litter. Cytogenetic evaluations revealed only the hypoprolific boar to have an abnormal karyotype, namely {38XY, t(1;14) (q2.12, q2.2)}. This represents a new type of 1;14 reciprocal translocation, and also the first report of a reciprocal translocation for swine in the United States.

Idiopathic hypereosinophilic syndrome in 3 Rottweilers.

Three Rottweilers with marked peripheral eosinophilia and infiltration of the liver, spleen, lungs, and bone marrow with eosinophils were diagnosed with idiopathic hypereosinophilic syndrome (IHES). Mean serum immunoglobulin E concentrations were markedly high. On cytogenetic analysis, no evidence of karyotypic abnormalities was found in bone marrow aspirates. Despite an extensive search, no underlying cause for the eosinophilia could be identified. In this study, cytogenetic analysis and measurement of serum IgE concentrations were used to differentiate IHES and eosinophilic leukemia.

X-chromosomal monosomy (77,X0) in a Doberman Pinscher with gonadal dysgenesis.

A 6-month-old stunted female Doberman Pinscher was found to have a 77,X0 chromosomal complement. The ovaries were small, consisting primarily of interstitial-type cells and solid epithelial cords. The dam, sire, and a male littermate had normal karyotypes.

In vitro viral expression as a criterion for development of control procedures for enzootic bovine leukosis.

In a university beef herd of 304 cattle in which six died of lymphosarcoma between 1980 and 1984, 77% of the Angus and 26% of the Charolais cattle were determined to be infected with bovine leukemia virus (BLV). Changes in iatrogenic procedures were initiated as early control measures. In vitro viral expression (VE) was used as a criterion to identify cattle for subsequent segregation or culling. This involved determinations of percentages of BLV-associated lymphocyte profiles among thin-sectioned Ficoll-Paque-isolated blood lymphocytes that were processed into plastic after culture for 48 h. Cattle retained until completion of nutritional studies or as breeding stock were separated into two groups. The BLV-seronegative cattle, BLV-seropositive cattle with 0% VE, and BLV-seropositive cattle with 1% to 4% VE were placed in group 1. Seropositive cattle with greater than or equal to 5% VE were placed in group 2. In 1985, evaluation of in vitro VE in 108 mature BLV-seropositive cattle retained for breeding revealed 36 (33%) had no observable VE. In 1986, 58 of 108 cattle were available to be reexamined, and 21 (36%) had 0% VE in both years. The VE expression values for individual cattle were generally comparable over the 2-year period. Of 48 initial seronegative breeding stock housed in group 1 with BLV-seropositive cattle with low or no VE, 21 (44%) seroconverted during 1985 to 1986. A positive correlation of 0.585 was found between VE and age-related absolute lymphocyte number.

XX/XY chimerism and freemartinism in a female llama co-twin to a male.

A 20-month-old female llama was examined because at the time of mating, the male llama was apparently unable to achieve intromission. The female llama had been born co-twin to a male. On physical examination, the vaginal vestibule appeared to end in a blind pouch, and the uterus, cervix, and ovaries could not be identified during transrectal palpation or ultrasonography. Karyotyping was done, and 43% of blood lymphocytes had 2 X chromosomes, and 57% had 1 X and 1 Y chromosome. All skin fibroblasts had 2 X chromosomes. A diagnosis of freemartinism and XX/XY chimerism was made. Because conception of twins may be more common in llamas than birth of twins, it is possible that freemartinism could develop in singleton females, if, for instance, a male twin was conceived and died after the placentas had anastomosed. More widespread use of karyotyping in llamas with congenital defects of the reproductive tract will help to define the incidence of freemartinism.

Prevalence of the 14/20 centric fusion chromosomal aberration in US Simmental cattle.

Cytogenetic evaluation was made on 353 Simmental cattle (166 male, 187 female) from 113 herds in 26 states. One hundred thirty-eight (39%) were found to be heterozygous-positive for the 14/20 centric fusion chromosomal translocation, including 41 (25%) males and 97 (52%) females. One submitted heparinized blood sample from a Simbrah bull was found to be positive for 14/20 and 1/29 centric fusions. Sampling, which was based on requests, was highly selective. Thus, the 39% prevalence found was not representative of 14/20 centric fusion in the national Simmental breed. On the basis of our findings, cytogenetic evaluation of breeding stock was consistent with modern management practice.

Triploidy (117,XXX) in a stillborn canine pup conceived with frozen semen.

Analysis of skin fibroblast cultures from a deformed stillborn female Alaskan Malamute pup revealed a 3n = 117,XXX (normal, 2n = 78,XX) chromosome count. The triploid pup was delivered by cesarean section 5 days after estimated date of parturition, because the bitch failed to start labor. The bitch had been inseminated with thawed frozen semen deposited into the lumen of the uterus approximately 4 days after ovulation. Gross anatomic abnormalities of the pup included omphalocele, diaphragmatic hernia, persistent right aortic arch, atresia ani, and no right forelimb distal to the scapula. The pup also had arthrogryposis of the left carpus, kyphosis of the thoracic vertebrae, widely separated cranial sutures, open fontanelles, hydrocephalus, and cleft palate. Suspected cause of the triploidy was dispermy of an aged oocyte after intrauterine deposition of the thawed frozen semen. Numeric chromosome abnormalities may be causes of fetal deformity or death that can be detected by fetal karyotype.