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High doses of adenotk were injected into the cerebrospinal fluid of rats and nonhuman primates (Macaca mulatta). Vector administration was followed by ganciclovir administration for 14 days. Despite the absence of clinical symptoms, analysis of the cerebrospinal fluid (CSF) and histopathological examination of the central nervous system (CNS) of the monkeys (3 weeks after vector injection) were consistent with a viral meningitis. Immunohistochemical analysis of the inflammatory infiltrates in the monkeys revealed the presence of T and B lymphocytes, indicating a combined cellular and humoral immune response to the vector. This latter was supported by the finding of intrathecal anti-adenovirus antibody synthesis. Rats receiving high intrathecal adenotk doses showed a transient and dose-dependent clinical toxicity consisting of lethargy, hyperemic eyes and weight loss. Histopathological examination of the meninges showed a shift from polymorphonuclear infiltrates during the first post-injection days to clusters of mononuclear cells after 7 days. Acute toxicity is probably related to the early, innate immune response to the vector. In a separate experiment, high levels of IL-8 and IL-6, were measured during the first 2-3 post-injection days in the CSF of two monkeys which received intrathecal adenoLacZ. Therefore, these cytokines seem to play an important role in initiating the nonspecific immune response. In one monkey which received adenotk, recombinant adenovirus was cultured from serum samples obtained at the 7th post-injection day. At this time-point, no vector could be isolated from CSF samples. Based on these preclinical data, we recommend careful dose finding for clinical studies that aim to treat patients with leptomeningeal metastases.

In the present paper the time course of brain tissue changes as evoked by a microdialysis probe and repeated dialysis procedures was examined by semiquantitative histology. The reactions to the presence of the probe as such were minimal. However, after more than two repeated perfusion procedures, tissue scores of hypercellularity and infiltration of granulocytes increased. It is concluded that the frequent use of repeated dialysis procedures may give rise to tissue effects parallelled by changes in BBB permeability. This has to be taken into account when intracerebral microdialysis is applied repeatedly within the same animal.

The use of intracerebral microdialysis as a tool to measure the penetration of anticancer agents in brain tumor was investigated.Following intravenous (iv) administration of 75 mg/kg. concentration-time profiles of methotrexate (MTX) were determined in brain cortical dialysate and in plasma. The individual ratio of the area under the curve of MTX in brain dialysate over that in plasma (MTX penetration) was determined in normal brain, in tumor-bearing brain and in brain after sham tumor implantation. Individual brains were examined histologically on the presence of tumor, as well as for other factors that might influence local MTX penetration. Histological scores were related to the individual data on penetration of MTX.MTX penetration values were higher in cortical brain at the site of the tumor, as compared to the levels measured in normal or sham implanted brain (mean increase to 250%). In the cortical brain contralateral to the tumor, MTX penetration values were found to be lower than in normal brain (mean reduction of 65%). Furthermore, it appeared that in the absence of tumor tissue, the presence of exudate around the probe was independently associated with increased penetration of MTX into the brain.Tumor tissue appeared to be the most important parameter in changing local MTX penetration in brain after tumor implantation. In general, it is anticipated that intracerebral microdialysis combined with histological examination can be used to investigate effects of brain tumor presence on regional (periprobe) penetration of anticancer drugs into the brain.

Bone is subject to continuous remodeling throughout life. The age-related loss of (trabecular) bone, leading to senile osteopenia, is mainly due to impaired bone formation. Osteoblasts (OB) and osteoclasts (OC) have been identified as playing a crucial role in the process of bone turnover, but the contribution made by their precursors is not well documented. We analyzed the cells of the osteoblast and osteoclast cell lineage along the trabecular bone of tibiae and the stromal cells in the marrow of aging BN/Bi Rij rats using electron microscopy. It appeared possible to distinguish preosteoblasts (pre-OB), OB, preosteoclasts (pre-OC), OC, and inactive bone-lining cells. Periods of increase, the maximal peak, and the decrease in trabecular bone volume were defined by means of morphometric measurements of trabecular bone volume. We found a decrease of more than 10-fold in the number of OB with age, but the numbers of pre-OB, pre-OC, and OC expressed per unit bone length, although variable, were age independent. The relative bone resorption and formation surface, expressed as a percentage of the total bone surface, decreased 2- and 15-fold, respectively. In 2-year-old animals the total volume of stromal cells, part of which constitutes the stem cell compartment of the osteogenic lineage, was a quarter of that found in 1-month-old animals and a third of that found in 6-month-old animals. The loss of trabecular bone is concomitant with a sharp increase in the ratio of pre-OB/OB, the ratio of OC/OB, and in the ratio of resorption to formation surfaces. There was no relation between the ratio of pre-OC/OC with age. These data lead to the conclusion that the main factor causing bone loss with age is a diminished maturation of pre-OB into OB.

The risks of total-body irradiation with large doses of X rays (average dose 6.7 Gy) and fission neutrons (average dose 3.4 Gy) were investigated by keeping a group of long-term surviving monkeys from an experiment on acute effects under continuous observation. On the basis of the number of animals developing tumors in each group as a function of the total observation period and the average absorbed dose, relative biological effectiveness (RBE) values between 4 and 5 have been derived at these high dose levels. In experiments on mammary carcinogenesis in rats the highest RBE values are observed for neutrons with energies of 0.43 to 1 MeV as produced by the p + T reaction or by the fission process. Based upon linear dose-response curves for neutrons and X rays, a maximum RBE value of 15 was observed for induction of adenocarcinomas in WAG/Rij rats. Appreciably higher RBE values would be obtained if the results of the gamma-ray exposure, indicating a nearly quadratic dose-response relationship, were used as a baseline. For radiation protection applications it should be realized, however, that such an increase will be caused by the lower efficiency of low-linear-energy-transfer radiation rather than by an increase in efficiency of the neutron irradiation at low doses.

One hundred and thirty-five sera from aged Mastomys were screened for the presence of spontaneously occurring autoantibodies using an indirect immunofluorescence technique. Such antibodies appeared to be relatively frequent and a number of different tissue specificities were observed. Autoantibodies observed were antibodies to cytoplasmic antigens in liver cells, thyroid follicular cells, and renal proximal tubular cells, striated and smooth muscle, gastric parietal cells, nuclear factors, colloid, and erythrocytes. Several antibody specificities were present in most sera, with a maximum of six and a median value of three different specificities per Mastomys. Anti-striational antibodies of the myasthenic type and anti-colloid antibodies belonged to the IgG class, antierythrocyte antibodies to the IgG and IgM classes, and the other types to the IgM class. From preliminary histopathological data it appears that of the spectrum of autoantibodies present in Mastomys, only autoantibodies directed to colloid could be associated with distinct histopathological changes (i.e., lymphoplasmacellular thyroiditis). Although striational antibodies as found in patients with myasthenia gravis were common in Mastomys, clinical signs of increased muscular weakness were lacking and antibodies to acetylcholine receptors were absent. The multiplicity of autoantibodies in this species together with other abnormalities in the immune system make Mastomys a promising model for the study of basic mechanisms underlying autoimmunity.

The incidence of spontaneously occurring tumors of the cervix and vagina was unusually high in an inbred strain of Brown Norway rats (BN/Bi). Fifty-four tumors were diagnosed in the cervixes or vaginas of 252 rats. Of the tumors, 7 were squamous cell carcinomas, 4 were leiomyomas, and the rest were sarcomas. These tumors were found in nearly 20% of all female rats that died naturally.

Sendai virus infected a hysterectomy derived, barrier maintained breeding colony and a conventional aging rat colony. The virus produced seroconversion in the colonies followed by a 7-month period of decreasing titers. Clinical signs were absent during the months when titers were highest, and there was no increase in mortality, but multifocal interstitial pneumonia with perivascular and peribronchial cuffing by lymphocytes and plasma cells was present in rat lungs examined histologically. Such lesions were absent before the period of seroconversion. During the months of declining titers, the interstitial and perivascular lesions decreased in frequency and severity. The peribronchial lesions did not decrease, however, and were still present in many rats 7 months after the acute infection. Attempts to isolate the virus from weanling rats were unsuccessful.

Although earlier reports in the literature suggested degenerative changes in the senescent hypothalamo-neurohypophyseal system (HNS), recent investigation showed hyperactivity of this system in the old Wistar (WAG/Rij) rat. In the brain, changes were found in those sites of extrahypothalamic vasopressin (VP) fiber termination that are testosterone-dependent. In the present study, further evaluation of these changes was performed in male Brown-Norway (BN/BiRij) rats. Immunocytochemical staining of VP binding sites in renal tubuli of the senescent, 33-month-old rats was occasional, and could only slightly be enhanced up to weak staining by in vitro preincubation with the peptide, in contrast to the intense staining observed in young, 3-month-old rats. Although VP plasma levels of young and old rats did not differ significantly and no change in either urine or plasma osmolality was observed, urinary VP concentration and 24-hour urinary VP excretion were significantly increased in senescent rats. The activation of the hypothalamo-neurohypophyseal system (HNS) in the senescent rat seems thus to compensate for a decreased responsiveness to VP in the aged kidney. Testicular weight in the senescent animals declined by 40% and a highly significant decrease of 80-90% was observed in total and free testosterone plasma levels. Consequently, changes in peripheral organs in senescent rats may well underly the changes observed in the brain of these animals.

Hydrogel was used to provide water in a solid state to rats and mice under laboratory conditions. Hydrogel was easy to handle and readily consumed by the animals. In studies extending over 10 months, no adverse effects on the condition of the animals were observed. Consumption of hydrogel as the sole source of water for nearly 2 months had no effect on the concentration of selected fecal aerobic microorganisms. Histopathological changes were not observed in the tissues of rats and mice kept for periods up to 7 months on hydrogel as the sole source of fluids. The survival time of rats and mice kept on hydrogel after exposure to supralethal doses of total body irradiation did not differ significantly from that of control animals given drinking water in bottles.

A naturally occurring, chronic disease of the respiratory tract was investigated from the time of its onset to completion of life-time studies in a colony of rats. The disease was characterized by peribronchial lymphoid cuffing, suppurative bronchitis, bronchiectasis and bronchial abscesses. Its onset in the colony occurred a few months after an epizootic of Sendai virus infection. Limited retrospective serological testing indicated that Mycoplasma pulmonis may have been present in the colony at that time and continued to persist throughout life in some rats in the colony. Although of uncertain significance, light and electron microscopy consistently demonstrated many filamentous bacteria between the cilia on respiratory epithelium and free in bronchial exudate in these cases. Attempts to culture this organism on artificial media were unsuccessful.

Five squamous cell carcinomas were induced in the lungs of WAG/Rij rats by radiation emitted from isotopes iridium-192 or iodine-125. Tumor fragments were transplanted subcutaneously in syngeneic hosts for propagation of the tumors. A lung cancer model based on implantation of tumor fragments in the lung has been developed. Tumor implants in the lung grew into large invasive squamous cell carcinomas. Metastases in the renal cortex were frequently observed. Tumor growth was determined from repeated chest radiographs. Volume changes after cytostatic treatment could be monitored accurately up to several months. Squamous cell carcinomas transplanted subcutaneously responded as heterogeneously to a variety of cytostatic drugs as did their human counterparts. Responses of the tumor line L17 to doxorubicin were similar when tumors were growing intrapulmonarily or subcutaneously. However, the response of L33 tumors to cisplatin was different, depending on the location. The tumors growing in the lungs provide a model for realistic testing of regimens involving radiation doses, cytostatic drugs, and combinations thereof.

Squamous cell carcinomas were induced in the lungs of male WAG/Rij inbred rats by radiation emitted from the isotopes iridium-192 or iodine-125. These isotopes were implanted by a surgical procedure in the lungs of young rats. Forty rats received implants of 192Ir wires and 20 animals, of 125I seeds. In a 14-month observation period, 30 of the 40 animals with implants of 192Ir wires developed tumors. Malignant hemangioendotheliomas occurred with the highest frequency (50%). From the lungs of 12 rats, squamous cell carcinomas were found. In the observation period of 17 months, 3 rats with implants of 125I seeds developed tumors, among which 1 squamous cell carcinoma could be identified. Tumor fragments were transplanted in syngeneic hosts for propagation of the tumors. Histologic appearances of tumors remained constant in subsequent passages. Responses of transplanted tumors growing in the flanks of syngeneic hosts to doses of radiation, methotrexate, or vinblastine were determined. Although the histologic appearances of the 5 squamous cell carcinomas were similar, tumor-doubling times and responses to irradiation and chemotherapeutic drugs were different. Small cell or large cell carcinomas were not observed.

Concanavalin A (Con A) and phytohemagglutinin (PHA) responses of spleen and blood lymphocytes from tumor-bearing (TB) rats were found to be markedly depressed in 4 different models employing tumors of spontaneous origin. Removal of phagocytic cells from both spleen and blood lymphocyte suspensions led to a complete restoration of the responses, indicating that the decreased responses were not due to intrinsic defects in the lymphocytes. The reduction was shown to be due to the inhibitory effect of an increase in the percentage of phagocytic cells. In addition, TB induced an atrophy of the thymus and a decrease in the number of thymic lymphocytes, mainly due to severe lymphocyte depletion in the cortex. The cells that remained in the thymus exhibited increased responsiveness to PHA and Con A as compared to thymus cells from normal rats. Similar results were found in hydrocortisone acetate-treated rats, suggesting that TB leads to a decrease in nonresponsive, cortical corticosteroid-sensitive thymocytes.