Evidence for resistance to MPTP in C57BL/6 x BALB/c F1 hybrids as compared with their progenitor strains

The neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is capable of producing a syndrome in mice which shares major characteristics with human Parkinson's disease. There is evidence for a genetic influence on the degree of damage exerted by MPTP, since different strains of mice can dramatically differ in their response to MPTP. We produced reciprocal F1 hybrids by crossbreeding the MPTP-susceptible C57BL/6 strain with resistant BALB/c. These hybrids were compared to the parental strains using neural and behavioral measures in order to characterize the genetic transmission of MPTP-susceptibility. The F1 generation as a whole had a lower depletion of neostriatal dopamine levels than even found in BALB/c. Furthermore, there was no significant loss of tyrosine hydroxylase-positive cells in the substantia nigra and quick recovery from deficits in motor behavior in F1, herein resembling BALB/c. We suggest that several loci are involved in susceptibility to MPTP, and that the trait is under control of recessive susceptibility and/or dominant resistance alleles, which interact in F1, leading to extremely low susceptibility.

Interaction of CPCCOEt with a chimeric mGlu1b and calcium sensing receptor

7-Hydroxyiminocyclopropan[b]chromen-1a-carboxylic acid ethyl ester (CPCCOEt) has previously been shown to be a selective non-competitive antagonist at the metabotropic glutamate (mGlu) receptor subtype 1. In this study we have tested the effect of CPCCOEt on mGlu1b, the calcium sensing receptor (CaR) and a chimeric receptor consisting of the agonist binding amino-terminal domain (ATD) of CaR and the seven transmembrane (7TM) domain of mGlu1b (named Ca/1b). CPCCOEt inhibited responses of (S)-glutamic acid and Ca2+ at mGlu1b and Ca/1b, applied at EC50 values, with IC50 values of 10.2 microM and 13.4 microM, respectively, whereas it was weak as an antagonist of Ca2+ at CaR. These data provides strong evidence that CPCCOEt exerts its antagonistic effect on mGlu1 solely by binding to the 7TM domain.

Allele-specific losses of heterozygosity on chromosomes 1 and 17 revealed by whole genome scan of ethylnitrosourea-induced BDIX x BDIV hybrid rat gliomas

The induction of neural tumors by N-ethyl-N-nitrosourea (EtNU) in inbred strains of rats has evolved as a valuable model system of developmental stage- and cell type-dependent oncogenesis. Tumor yield and latency times are strongly influenced by genetic background. Compared with BDIX rats, BDIV rats are relatively resistant to the induction of brain tumors by EtNU, with a lower tumor incidence and latency periods prolonged by a factor of 3. To characterize genetic abnormalities associated with impaired tumor suppressor gene function in neuro-oncogenesis, losses of heterozygosity (LOHs) and microsatellite instability (MI) were investigated in brain tumors induced by EtNU in (BDIV x BDIX) F(1) and F(2) rats. The polymerase chain reaction was used to amplify 55 polymorphic microsatellite markers spanning the entire rat genome. The tumors displayed different histologies and grades of malignancy, corresponding to part of the spectrum of human gliomas. MI was not observed in any of the tumors. LOH of rat chromosome 1q was predominantly detected in oligodendrogliomas and mixed gliomas, with a 30% incidence in informative cases. 11p15.5, the human genome region syntenic to the consensus region of LOHs observed on rat chromosome 1, has been shown to be involved in the formation of gliomas in humans. Furthermore, rat brain tumors of different histologies often showed allelic imbalances on chromosome 17p. In both cases of LOH, there was a clear bias in favor of the parental BDIV allele, suggesting the involvement of tumor suppressor genes functionally polymorphic between the two rat strains.

Lymphohematopoietic graft-vs.-host reactions can be induced without graft-vs.-host disease in murine mixed chimeras established with a cyclophosphamide-based nonmyeloablative conditioning regimen

Mixed hematopoietic chimerism can be induced in mice receiving allogeneic bone marrow transplantation (BMT) after nonmyeloablative host conditioning with depletion T cells with of anti-T cell monoclonal antibodies (mAbs), low-dose (3 Gy) total-body irradiation (TBI), and local thymic irradiation (7 Gy). These mice are specifically tolerant to donor and host antigens. When nontolerant donor T cells are given to chimeras several months after BMT, full donor-type chimerism develops, but graft-vs.-host disease (GVHD) does not occur. The induction of such lymphohematopoietic GVH reactions without GVHD could provide an approach to separating graft-vs.-leukemia (GVL) from GVHD in patients with hematologic malignancies. To make the nonmyeloablative conditioning regimen described above more cytoreductive for such malignancies, we have now modified it by replacing TBI with cyclophosphamide (CP). Treatment with anti-CD4 and anti-CD8 mAbs on day -5, 200 mg/kg CP on day -1, and 7 Gy thymic irradiation on day 0 was only slightly myelosuppressive and allowed fully major histocompatibility complex (MHC)-mismatched (with or without multiple minor antigen disparities) allogeneic bone marrow to engraft and establish long-term mixed chimerism in 40 to 82% of recipients in three different strain combinations. The administration of nontolerant donor spleen cells at 5 weeks or at 5, 8, and 11 weeks posttransplant was capable of eliminating host hematopoietic cells, leading to full or nearly full donor chimerism in six of six and two of four chimeric animals in two different strain combinations. No clinical evidence of GVHD was observed in any recipients of these donor leukocyte infusions (DLI). These studies demonstrate that induction of mixed chimerism with nonmyeloablative conditioning followed at appropriate times by DLI might allow lymphohematopoietic GVH reactions, and hence GVL effects, to eliminate chronic hematologic malignancies without causing clinically significant GVHD.

Multivesicular body morphogenesis requires phosphatidyl-inositol 3-kinase activity

Multivesicular bodies are endocytic compartments containing multiple small vesicles that originate from the invagination and 'pinching off' of the limiting membrane into the luminal space [1] [2] [3]. The molecular mechanisms responsible for the formation of these compartments are unknown. In the human melanoma cell line Mel JuSo, newly synthesised major histocompatibility complex (MHC) class II molecules accumulate in multivesicular early lysosomes [4]. The phosphatidylinositol (PI) 3-kinase inhibitor wortmannin induced the transient vacuolation of early MHC class II compartments, but also of early and late endosomes. We demonstrate that endocytic membrane influx is required for the wortmannin-induced swelling of vesicles. The wortmannin-induced vacuoles contained a reduced number of intraluminal vesicles that were linked to the limiting membrane by membraneous connections. These data suggest that wortmannin inhibits the invagination and/or pinching off of intraluminal vesicles and provide evidence of a role for PI 3-kinase in multivesicular body morphogenesis. We propose that the wortmannin-induced vacuolation occurs as a result of the inability of multivesicular bodies to store endocytosed membranes as intraluminal vesicles thereby causing the formation of large 'empty' vacuoles.

IFN-gamma-mediated prevention of graft-versus-host disease: pharmacodynamic studies and influence on proliferative capacity of chimeric spleen cells

Recently we demonstrated that prolonged administration of IFN-gamma prevented the development of GVHD in a MHC-mismatched murine BMT model. Treatment with IFN-gamma allowed the development of mature donor-derived allo-tolerant immunocompetent cells in complete chimeric recipients. Here we present data on the pharmacodynamics of this cytokine-mediated protection against GVHD. Treatment with 50000 U IFN-gamma twice weekly for a period of 5 weeks, starting at the day of BMT, was shown to be the optimal treatment protocol, resulting in complete prevention of GVHD-related mortality. Treatment during 1 week with a three-fold higher weekly dose of IFN-gamma (50000 U six times) did not result in significantly improved survival. The start of IFN-gamma administration was a critical factor since a delay of 3 days from the time of BMT resulted in substantial GVHD-induced mortality. Furthermore, it was shown that IFN-gamma treatment inhibited the spontaneous and Con-A-induced proliferation of T cells at 7-14 days after BMT, which is the critical period for the initiation of acute GVHD. However, long-term survivors after IFN-gamma treatment showed a recovery of immunity in contrast to long-term survivors of saline-injected animals, as tested by Con-A responsiveness. It seems that injection of high dose IFN-gamma suppresses the response of potentially alloreactive donor T cells during what normally is the initiation phase of the GVH reaction (GVHR), resulting in the abrogation of GVHD.

Role of tumor necrosis factor-alpha in the spontaneous development of pulmonary fibrosis in viable motheaten mutant mice

The viable motheaten mutant mouse is severely immunodeficient and dies from a naturally occurring progressive pulmonary inflammation at approximately 10 weeks of age. The pulmonary disease is characterized by excessive macrophage accumulation in the lung and fibrosis. We correlated the development of lung injury in viable motheaten mice with tumor necrosis factor-alpha (TNF-alpha) levels in serum and lung. Significantly increased serum TNF-alpha levels were observed by enzyme-linked immunosorbent assay in viable motheaten mice at 4, 6, and 10 weeks of age as compared with normal control littermate mice. These ages correlated well with observed changes in lung wet weights, lung collagen content, and histological evidence of pulmonary inflammation and fibrosis. Qualitative assessment of lung tissue TNF-alpha levels was performed by immunohistochemical staining using immunoperoxidase techniques. These studies revealed increased levels of TNF-alpha in macrophage-like cells in viable motheaten mice from 5 to 10 weeks of age as compared with littermate control animals. Alveolar macrophages isolated from viable motheaten mice produced significantly greater amounts of TNF-alpha when stimulated with lipopolysaccharide compared with alveolar macrophages from control animals. In addition, administration of anti-TNF-alpha antibody to motheaten bone marrow recipient mice decreased the severity of acute lung injury. The results demonstrate a close correlation between the development of pulmonary injury and TNF-alpha levels in this model of spontaneously developing fibrotic lung disease.

Synergistic neutralization of a chimeric SIV/HIV type 1 virus with combinations of human anti-HIV type 1 envelope monoclonal antibodies or hyperimmune globulins

A panel of 14 human IgG monoclonal antibodies (MAbs) specific for envelope antigens of the human immunodeficiency virus type 1 (HIV-1), 2 high-titer human anti-HIV-1 immunoglobulin (HIVIG) preparations, and 15 combinations of MAbs or MAb/HIVIG were tested for their ability to neutralize infection of cultured human T cells (MT-2) with a chimeric simian immunodeficiency virus (SHIV-vpu+), which expressed HIV-1 IIIB envelope antigens. Eleven MAbs and both HIVIGs were neutralizing. When used alone, the anti-CD4-binding site MAb b12, the anti-gp41 MAb 2F5, and the anti-gp120 MAb 2G12 were the most potent. When combination regimens involving two MAbs targeting different epitopes were tested, synergy was seen in all paired MAbs, except for one combination that revealed additive effects. The lowest effective antibody concentration for 50% viral neutralization (EC50) and EC90 were achieved with combinations of MAbs b12, 2F5, 2G12, and the anti-V3 MAb 694/98D. Depending on the combination regimen, the concentration of MAbs required to reach 90% virus neutralization was reduced approximately 2- to 25-fold as compared to the dose requirement of individual MAbs to produce the same effect. Synergy of the combination regimens implies that combinations of antibodies may have a role in passive immunoprophylaxis against HIV-1. The ability of SHIV to replicate in rhesus macaques will allow us to test such approaches in vivo.

[Overcoming the "2-cell block" in mouse embryos in aggregation chimeras]

The embryos of the inbred mouse strain BALB/c are predisposed to so-called "two-cell block" after explantation from the maternal organism before the late two-cell stage and cultivation in a standard synthetic medium. Hybrid embryos (CBA x C57B1) F2 are competent to complete preimplantation development in vitro. The BALB/c embryo predisposed to block ("blocking") at the early two-cell stage was aggregated using phytohemagglutinin with four to five two- and eight-cell BALB/c embryos capable of reaching the blastocyst stage in vitro ("non-blocking"). This aggregate successfully developed until the blastocyst stage for 72 h. The aggregation of the early two-cell BALB/c embryos with each other did not prevent the block. After the aggregation of the blocking and non-blocking embryos at the two-cell stage, a common integrated blastocyst developed. In aggregates with eight-cell embryos, the blocking embryo formed a separate blastocyst, although it preserved contacts with non-blocking embryos during the entire period of cultivation. Ultrastructural analysis has shown that two-cell embryos aggregated using phytohemagglutinin form adhesive contacts up to several microns long. Possible mechanisms of cooperation between the competent and deficient partners in aggregates with two-cell embryos are discussed.

Induction of diabetes in NOD<-->C57BL/6 embryo aggregation chimeras by cyclophosphamide through preferential depletion of C57BL/6 lymphocytes

The majority of embryo aggregation (EA) mouse chimeras between non-obese diabetic (NOD) mice and C57BL/6 (B6) mice show clear signs of insulitis frequently accompanied by beta-cell destruction. Less than 5% of these chimeras, however, spontaneously progress to autoimmune diabetes, an incidence far lower than observed in NOD mice. The resistance in chimeras can be accounted for by the target organ chimerism and/or the immune system chimerism. To investigate the mechanism(s) controlling diabetes resistance in these mice, we studied a total of 92 NOD<-->B6 EA chimeras that showed overt lymphoid chimerism and treated 34 chimeras with cyclophosphamide (CY), a compound known to precipitate an acute form of insulin-dependent diabetes mellitus (IDDM) in pre-diabetic NOD mice, by interfering with regulatory mechanisms. We found that CY-treated EA chimeras displayed an increase in the NOD:B6 lymphocyte ratio and 32% of them developed diabetes that could be adoptively transferred to irradiated NOD or NOD-rag-2-/- mice. These findings suggest that lymphocyte chimerism rather than beta-cell chimerism accounts for diabetes resistance in NOD<-->B6 EA chimeras and that the susceptibility to CY-induced diabetes may be related to the proportion of NOD versus B6 lymphoid cells.

Morphological studies on avian spinal cord chimeras

Spinal cord chimeras were constructed by orthotopic grafting of quail embryonal neutral folds, neural crest and neural tube into chicken embryos. The spinal cord xenografts were accepted for varying lengths of time, but most chimeras eventually rejected the quail transplant. This was associated with perivenular cuffing and demyelination with preservation of most neurons, as well as clinical neurological symptoms. Twenty-four chimeras were studied to delineate the time of first appearance of glial deposits of immunoglobulin and to identify the subpopulations of T cells in spinal cord infiltrates. The results suggested that deposits of immunoglobulins on glial elements preceded inflammatory cell infiltration. The perivenular cuffs consisted predominantly of T cells and showed a preponderance of CD8- over CD4-positive cells (CD4/CD8 ratios around 0.6). Further, CD4+ cells were found almost exclusively in the central portions of the infiltrate, with the periphery consisting almost only of CD8+ cells. The diffuse cellular infiltrate of the parenchyme contained T and plasma cells. The T cells were almost exclusively CD8+. Plasma cells were seen only at the outer borders of the cuffs and dispersed throughout the quail-derived spinal cord tissue. It seemed that rejection of quail-derived melanocytes in feathers ('quail-like feathers'), described by us earlier, often preceded neurological symptoms and showed a histopathological pattern comparable to spinal cord lesions, i.e., predominantly perivascular cuffing. In preliminary studies, enhancement of disease by immunization with quail organ suspension and decreased intensity of disease by combined immunosuppressive treatment with FK 506 and cycylophosphamide were suggested. The data presented here are compatible with the hypothesis that rejection of CNS quail tissue by chimeras is preceded in the periphery by rejection of melanocytes in segments of skin and in feathers, and that the spinal cord rejection relies on xenoantibodies and on cytotoxic as well as delayed hypersensitivity-type T cells. Finally, these data strengthen the analogy between the histopathologic presentation and immune effector composition of the xenograft rejection lesions in the chimeras and the plaques seen in patients with multiple sclerosis.

The microenvironment created by non-blocking embryos in aggregates may rescue blocking embryos via cell-embryo adherent contacts

Under our culture conditions, mouse embryos from the BALB/c inbred mouse strain develop successfully in culture only from the late 2-cell stage onwards (so-called 2-cell block), whether or not EDTA is added to the culture medium. (CBA x C57BL) F2 embryos do not exhibit a 2-cell block. Medium conditioned by culture of non-blocking embryos from the 2-cell to the 8-cell stage did not improve the development of blocking embryos, nor did co-culture of blocking and non-blocking embryos, with or without conditioned medium. On the other hand phytohaemagglutinin (PHA)-assisted aggregation of an early 2-cell BALB/c embryo with five surrounding non-blocking F2 embryos (2-cell or 8-cell) or five BALB/c 8-cell embryos allowed the early 2-cell BALB/c embryos to develop into blastocysts within 72 h. Aggregation of blocking BALB/c 2-cell embryos with each other had no 'rescue' effect. When blocking and non-blocking 2-cell embryos were aggregated together, an integrated blastocyst was formed; but when the early 2-cell BALB/c embryos were aggregated with non-blocking 8-cell embryos, the blocking embryos formed a separate small blastocyst, which nonetheless retained adherent contact with the non-blocking embryos throughout the culture period. Ultrastructural analysis showed that 2-cell embryos aggregated with the aid of PHA form close adherent cell contacts up to several micrometres in length.

The induction of skin xenograft tolerance in rat-to-mouse combination could be affected by DFR mediating cells and antibodies against rat bone marrow cells as well as NK cells in the cyclophosphamide-induced tolerance system

We investigated whether the prolongation of skin xenograft survival was obtained by a tolerance-inducing method using cyclophosphamide (CY), by which long-lasting skin allograft tolerance could be induced. The long-lasting skin allograft survival could be obtained in the recipient C3H/HeN (C3H) mice which were given 100 micrograms of anti-CD4 mAb on day -3, 1 x 10(8) spleen cells (SC) plus 3 x 10(7) bone marrow cells (BMC) derived from C57BL/6 (B6) mice on day -2,200 mg/kg CY on day 0, and which were grafted with allogeneic B6 skin on day 14. When the C3H mice were treated with anti-CD4 mAb, 1 x 10(8) s.c. plus 5 x 10(7) BMC derived from F344 rat and CY, the F344 skin grafts survived slightly longer (about 15 days) than those in untreated recipients (about 8.4 days). Such a prolongation of skin xenograft survival was considered donor-specific because rejection of 3rd party skin grafts from BN rats occurred significantly earlier than that of F344 skin grafts. In the recipient C3H mice treated with anti-CD4 mAb, F344 s.c. plus BMC and CY, mixed chimerism in the periphery was detected for a few days after CY administration, although intrathymic chimerism was not detected throughout this study. In these recipient C3H mice, cytotoxic T lymphocytes (CTL) against F344 antigens were completely abrogated through the delayed footpad reaction (DFR) remained at a low but significant level. Moreover, though antibody (Ab) activity against F344 s.c. was completely abrogated, neither Ab activity against F344 BMC, which seemed to have a background common to natural Ab activity, nor NK activity were abrogated by this treatment. These results suggested that DFR mediating cells directly mediated skin xenograft rejection in the recipient mice treated with anti-CD4 mAb, F344 cells, and CY. Such cells may interfere with establishment of mixed chimerism and long-lasting skin xenograft tolerance, presumably in cooperation with CY-resistant Ab activity and NK cells.

Anti-CD3 treatment facilitates engraftment of full H-2-disparate donor bone marrow cells and subsequent skin allograft tolerance

The aim of the present study was to induce engraftment of full H-2-disparate donor bone marrow cells and the development of subsequent transplantation tolerance. To this end, recipient H-2b mice were treated with anti-CD3 and on the same day received 6 Gy whole body irradiation as well as donor bone marrow cells (H-2d). Anti-CD3 treatment was chosen because it results in suppression of T cell function and in the release of CSF associated with enhancement of donor bone marrow engraftment. Stable, long-term chimerism measured in peripheral blood and mesenteric lymph nodes was obtained using this preparative regimen. In contrast, the use of anti-CD3 F(ab')2 fragments failed to induce donor bone marrow cell engraftment, suggesting indeed an important role of anti-CD3-mediated growth factor production in marrow engraftment. To overcome the side effects of anti-CD3 treatment (cytokine release syndrome), anti-CD4 was given 1 day before the treatment protocol. Omission of anti-CD3 resulted in failure of donor bone marrow engraftment, indicating the essential role of anti-CD3 treatment in marrow engraftment. Skin transplantation performed 2 and 6 months after this well-tolerated conditioning regimen showed indefinite survival of first and second grafts, respectively. In addition, specific CTL nonresponsiveness developed, demonstrating the presence of classical transplantation tolerance across a full H-2 barrier.

Antiestrogenic effects of all-trans-retinoic acid and 1,25-dihydroxyvitamin D3 in breast cancer cells occur at the estrogen response element level but through different molecular mechanisms

Most breast tumors show estrogen-dependent growth and are thus susceptible to antiestrogenic therapy. MCF-7 cells, obtained from a human estrogen-dependent breast carcinoma, are widely used for studying the modulation of estrogenic responses by different effectors. All-trans-retinoic acid (RA) and 1,25-dihydroxyvitamin D3 (Vit D3) inhibited estrogen-induced growth of MCF-7 cells and their effect was potentiated by the classical antiestrogen, hydroxytamoxifen. In MCF-7 cells, we found that RA and Vit D3 also inhibited estrogen-induced transcription; this was shown both for an endogenous gene (pS2) and for various exogenous transfected genes. Their inhibitory effect could not be reversed by increasing estradiol concentrations, showing that contrary to classical antiestrogens, they did not compete with estradiol to bind the estrogen receptor (ER). Analysis of the inhibitory mechanisms indicates that RA and Vit D3 receptors can directly or indirectly impair the binding of ER to the estrogen responsive element. The antagonist effect of RA would be found especially at DNA level since it seems to essentially involve an estrogen responsive element. The antagonist effect of Vit D3 would be found especially at the ER level since it seems to concern estrogen binding and dimerization domains of ER. We conclude that the antiestrogenic effects of RA and Vit D3 are similar since they can, via their receptors, interfere with estrogenic action at the estrogen responsive element level but that they are not identical since different molecular mechanisms are involved.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) accelerates differentiation of murine preimplantation embryos in vitro

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a potent teratogen in several animal species, especially during the period of organogenesis. The purpose of this study was to test the hypothesis that TCDD has direct effects on the earliest stages of murine embryonic development, namely the preimplantation stages. Three endpoints were measured: 1) embryo cell number, a measure of embryo viability, 2) competitive embryonic cell proliferation utilizing chimeric embryos, another measure of embryo viability, and 3) cavitation rate, a functional measure of trophectoderm differentiation. Neither embryo cell numbers nor competitive embryonic cell proliferation (chimera assay) were affected by TCDD, either when the mother was dosed in vivo (prior to fertilization), or when 2-cell embryos were dosed in vitro. However, cavitation rates of in vitro-dosed embryos, in the presence of 10% fetal bovine serum, were significantly higher for TCDD than controls, suggesting that TCDD accelerated differentiation of murine preimplantation embryos. Taken together, these results demonstrate that: 1) TCDD can act directly on the murine preimplantation embryo, and 2) TCDD's actions are primarily on accelerated differentiation and not on embryo viability. To our knowledge, this is the earliest stage of mammalian development during which TCDD has been shown to exert an effect.

Involvement of the carboxyl-terminal region in modulation by TPA of the NMDA receptor channel

The epsilon 1/zeta 1 and epsilon 2/zeta 1 heteromeric N-methyl-D-aspartate (NMDA) receptor channels expressed in Xenopus oocytes, but not the epsilon 3/zeta 1 and epsilon 4/zeta 1 channels, are positively modulated by the treatment with 12-O-tetradecanoyl phorbol 13-acetate (TPA). Failure of potentiation in the presence of staurosporine suggests the involvement of protein kinases in the TPA effect. To identify the structural domain involved in the modulation of the NMDA receptor channel by the TPA treatment, we constructed chimeric subunits between the epsilon 2 and epsilon 3 subunits. Functional analysis of heteromeric channels containing chimeric epsilon subunits has shown that the carboxyl-terminal region of the epsilon 2 subunit is responsible for the activation of the epsilon 2/zeta 1 channel by the TPA treatment.

Ethylene glycol monomethyl ether (EGME) exposure of male mice produces a decrease in cell proliferation of preimplantation embryos

In this study using an aggregation chimera assay we examined male mice exposed to a nonmutagenic reproductive toxicant, EGME, for the transmission of impaired viability to their progeny preimplantation embryos. Prior to their aggregation into pairs, one of the embryos was labeled with a viable dye fluorecein isothiocyanate (FITC) to determine the relative cellular contribution from each partner embryo when chimeras were dissociated 30 to 35 h later (2 to 3 cell cycles). Direct cell-cell contact of embryos derived from exposed males and embryos from control males creates a competitive situation that has been shown to confer a cell proliferation disadvantage to the embryo from an exposed parent. The cell proliferation disadvantage is expressed as a "proliferation ratio": number cells from an experimental embryo/total chimera cell number. Male mice were exposed to EGME by gavage for 5 days with 0, 50, 200, 750, or 1500 mg/kg and were serially mated with unexposed female mice for the next 7 weeks. Proliferation ratios were significantly decreased in the 50, 200, and 750 mg/kg dose groups at week 4, which corresponds to the pachytene spermatocyte stage of spermatogenesis. Proliferation ratios were also significantly decreased in the 1500 mg/kg group at week 5. Due to transient infertility in this dose group, there were not sufficient numbers of embryos to evaluate for week 4. These results indicate that male mice exposed to EGME transmitted adverse effects to their progeny embryos that were expressed as an embryonic cell proliferation disadvantage in the chimera assay.

Cardiovascular anomalies in chick embryos produced by bis-diamine in dimethylsulfoxide

N,N'-bis(dichloroacetyl)-1,8-octamethylenediamine(bis-diamin e) (100 micrograms) dissolved in dimethylsulfoxide (DMSO) was administered to early developing chick embryos (Hamburger-Hamilton stage 9-21) in order to clarify the teratogenic effects on the cardiovascular system and to determine whether bis-diamine interferes with the migration of neural crest cells. Of 346 cases, 154 (44.5%) survived. The incidence of cardiovascular anomalies was 149 out of 154 cases (96.8%). Infundibular ventricular septal defect, double outlet right ventricle, and persistent truncus arteriosus were the primary cardiac anomalies observed in this study. A high percentage of these anomalies were accompanied by hypoplasia of the right 6th aortic arch artery and persistent left 4th aortic arch artery. Particularly, administration of bis-diamine to chick embryos at stage 13 resulted in a high incidence of persistent truncus arteriosus (64.3%). Bis-diamine has been suspected to inhibiting the migration of neural crest cells. However, neural crest cells were observed in the tunica media of the great arteries and the truncal valves of persistent truncus arteriosus produced by bis-diamine in chimeric embryos at stage 13. Morphological changes such as cell death were not observed.

Enhanced intraspecific protoplast fusion in yeast

Intraspecific hybrid production from the polyethylene glycol induced fusion of yeast protoplasts was greatly increased when calcium propionate was included as the source of the requisite Ca2+. The use of calcium propionate, as opposed to the more commonly employed calcium chloride, resulted in substantially greater yields of hybrids from intraspecific fusions of protoplasts of Saccharomyces cerevisiae and Candida albicans. It is postulated that the ability of calcium propionate to enhance the fusion frequency is due to the anion binding to the etheric oxygen of PEG and potentiating the fusogenicity of the polymer.

Establishment of donor hematopoiesis after hydroxyurea-induced aplasia following allograft failure in a patient with monosomy 7 variant of childhood chronic myelogenous leukemia

Monosomy 7 variant childhood chronic myelogenous leukemia (CML) is a rare, fatal leukemia that usually terminates in blast crisis. We report successful marrow transplantation in a patient with this disease using his one HLA locus mismatched mother. Initially following transplant the patient exhibited mixed hematopoietic chimerism, cytogenetic relapse, and clinical relapse of leukemia. However, following recovery from a period of hydroxyurea-induced aplasia, marrow studies showed elimination of the mixed chimerism, absence of the 45,XY,-7 leukemic clone and full engraftment with donor marrow (46,XX). The ability of hydroxyurea to eliminate mixed chimerism in favor of donor hematopoiesis and to eliminate the persistent leukemic clone in this patient with CML suggests treatment approaches worthy of future investigation.

Ouabain sensitivity of a chimeric alpha subunit (Torpedo/rat) of the (Na,K)ATPase expressed in Xenopus oocyte

A cDNA for a chimeric alpha subunit of the (Na,K)ATPase was constructed and expressed in Xenopus oocytes in order to elucidate structural features involved in ouabain sensitivity. A chimeric alpha subunit, in which the N-terminal 165 amino acid sequence of ouabain-resistant rat alpha subunit, including the first two transmembrane segments (M1 and M2), was replaced by a sequence from the corresponding region of ouabain-sensitive Torpedo alpha subunit, was ouabain-sensitive, suggesting that the M1-M2 junction is a site responsible for ouabain sensitivity of the (Na,K)ATPase.

Drug-induced tolerance to allografts in mice. XII. The relationships between tolerance, chimerism, and graft-versus-host disease

When AKR/J Sea (AKR, H-2k) mice were primed i.v. with 1 X 10(8) viable spleen cells from naive C3H/He Slc (C3H, H-2k) mice and treated i.p. with 200 mg/kg cyclophosphamide (CP) 2 days later, a minimal degree of mixed chimerism associated with tolerance to C3H skin was established without graft-versus-host disease (GVHD) and maintained for at least one month. When AKR mice were primed i.v. with 1 X 10(8) viable spleen cells from C3H mice preimmunized i.v. 7 days earlier with 5 X 10(7) viable AKR spleen cells, and treated with 200 mg/kg CP, chimerism became exclusive, but lethal GVHD occurred in the AKR mice. Moreover, most of normal AKR mice primed with the preimmunized C3H spleen cells without CP died of GVHD. In contrast, in a major histocompatibility complex (MHC)-incompatible combination of AKR (H-2k)-C57BL/6 Cr Slc (B6, H-2b), mixed chimerism, tolerance to skin allografts, and GVHD were not observed, whether or not the mice had been treated with naive or preimmunized B6 spleen cells with or without CP.

The effect of retinoic acid pretreatment on the ability of murine embryonal carcinoma and inner cell mass cells to participate in chimaera development

Certain embryonal carcinoma (EC) cell lines can colonize the embryo following blastocyst injection or embryo aggregation, giving rise to EC-embryo chimaeras. However, such chimaeras often develop abnormally. For example, diploid P19 cells colonize the embryo readily but resulting chimaeras are usually abnormal, with persistence of tumour cells. Retinoic acid (RA) induces differentiation of EC cells to a variety of cell types in vitro but, in this study, it was shown that pretreatment of P19 cells with RA did not result in more normal development of P19-embryo chimaeras. The only significant effect of RA was to reduce the ability of P19 cells to participate in embryonic development at all after blastocyst injection. RA did not have a direct toxic or teratogenic effect on preimplantation mouse embryos and did not affect the ability of pluripotent embryo cells to colonize chimaeras. Therefore, RA may not be the normal inducer of differentiation in early embryogenesis.

The effect of limited courses of cyclosporine on survival and immunocompetence of allogeneic bone marrow chimeras

Isolator-maintained CBH/Ola (Rtlc) rats were lethally irradiated and reconstituted with spleen and bone marrow cells from fully allogeneic WAG or Wistar (Rtlu) donors. Hematopoietically reconstituted rats were treated with cyclosporine (CsA)4 as prophylaxis for graft-versus-host disease (GVHD) for periods ranging from 6 to 26 weeks. Following the termination of CsA treatment GVH reactivity developed in all recipients of allogeneic cells regardless of the duration of immunosuppression. Approximately a third of the reconstituted rats survived the post-CsA period of GVH activity; these rats carried peripheral lymphocytes and spleen cells of donor strain origin and were specifically unresponsive to donor strain skin grafts. Surviving chimeras remained healthy for long periods (up to 18 months) after transplantation, although morbidity increased slightly for rats moved to normal animal house conditions. However, all chimeras had some degree of lymphopenia and showed diminished immunological responses to extraneous antigens and third-party skin grafts. Experiments to elucidate the mechanisms by which specific tolerance was maintained in chimeras indicated that neither the deletion of host-reactive lymphocytes from the graft nor an absence of host bone-marrow-derived "stimulator" cells was responsible. It was shown that the potential GVH reactivity of normal donor strain cells was specifically suppressed in vivo (in the chimera) and that this suppression could be transferred to secondary irradiated recipients by transferring chimeric spleen cells. Attempts to demonstrate a role for suppressor cells in the maintenance of the chimeric state yielded inconclusive results.

Increased incidence of malignant tumors in dogs after total body irradiation and marrow transplantation

One hundred fifty-three dogs were given 6.1-21.3 Gy total body irradiation at 0.02-0.2 Gy/minute delivered from two opposing cobalt sources followed by allogeneic (131 dogs) or autologous (22 dogs) marrow grafts and observed for 6-127 (median 33) months. The incidence of malignant tumors in radiation chimeras was compared to that in 242 untreated dogs observed for 6-188 (median 81) months. Thirteen malignancies were observed in 11 radiation chimeras. These tumors included two leiomyosarcomas of the mesentery, four adenocarcinomas of the breast, prostate and ovary, two mastocytomas, one hypernephroma, perianal gland carcinoma, seminoma, Brenner tumor, and an oligodendroglioma. Fifty-four malignancies were seen in 44 control dogs. These included 12 mammary carcinomas, 12 thyroid carcinomas, six lymphomas, two malignant melanomas, and a number of other solid tumors. On the basis of time-dependent Cox regression analysis, radiation chimeras had an estimated relative risk of developing a malignancy that was 5-fold higher than in control dogs (p less than 0.001). No tumor has yet been observed in a group of 15 chimeras conditioned by cyclophosphamide or dimethyl busulfan and followed for 6-97 (median 24) months. The increased risk of cancer among canine radiation chimeras suggests that high-dose total body irradiation may increase the risk of developing a malignancy and should be avoided whenever possible in the conditioning for marrow transplantation of human patients with nonmalignant diseases.

Effect of concanavalin A on the formation of the mouse blastocyst

Culture of precompact zona-free mouse embryos in the plant lectin concanavalin A (Con A) at 20 micrograms/ml inhibits blastocyst formation. Cell division is retarded compared with control embryos, compaction of the morula is prevented, and fluid accumulation occurs within but not between cells. As little as two hours of incubation in Con A can cause developmental delay and an eventual increased incidence of lysis, and although embryos can recover from more prolonged pulses of Con A, the blastocysts formed are often abnormal. Blastocyst formation occurs in some embryos, but does not do so unless at least some cells have undergone a fifth round of cell division before incubation in the lectin. However, not all embryos that contained more than 32 cells compacted and showed intercellular fluid accumulation in Con A. Thus, blastocyst formation is not restricted solely by an inhibition of cell division or a reduction in cell number, but is also impaired by interference of the lectin with the cell surface and its interactions. Morulae bind divalent Con A and monovalent succinyl-Con A similarly, but developmental interference is absent with the latter, suggesting that divalent Con A acts through a cross-linking of surface receptors.

Latent period and yield of chemically-induced skin tumors in chimeric mice

The induction of skin tumors in chimeras produced by 2 methods and between 2 different parental sets was investigated. The yield and latent period of the tumors were compared in the several types of chimeras. In chimeras between strains of mice with long and short latent periods, a short latent period was obtained. Some of the tumors in these animals were derived from the late-responding cell type. The presence of cells from 2 strains in a single animal may modify the latent period of the late responding strain-derived cells in the chimeras.

Cell-mediated immunity in canine marrow graft recipients given cyclophosphamide

The cellular immune status of 48 canine chimeras was studied between 15 days and 3 years after a lethal dose of cyclophosphamide (CY) and an allogeneic marrow graft. Marrow graft recipients were given no further immuno-suppressive treatment. Recovery of total white blood cell counts was complete by day 20 after grafting. Peripheral blood lymphocyte counts did not reach the normal range until day 100. Short-term chimeras (less than 100 days postgrafting) showed marked impairment of cell-mediated immunity as indicated by the inability to respond adequately to nonspecific mitogenic (PHA, ConA, PWM) and specific antigenic (allogeneic lymphocytes, PPD) stimulation in vitro. Skin test reactivity to PPD after immunization with BCG was also significantly depressed. Long-term chimeras (more than 100 days postgrafting) had normal in vitro response to mitogens; lymphocyte blastogenesis to specific antigens however remained decreased for prolonged periods postgrafting. The survival time at first set allogeneic skin grafts showed no significant difference between chimeras and normal control dogs. Lymphocyte transformation in response to stimulation with specific antigens may prove a useful parameter for the in vitro evaluation of defects in cellular immune reactivity following allogeneic marrow transplantation.

[Organ tolerance and incomplete bone marrow chimera in dogs]

Cyclophosphamide-induced chimeras develop organ tolerance as do radiation chimeras, as long as hemopoietic cells of donor origin are detectable, independent of the degree of chimerism (n = 7). 4 of 7 dogs with reversion of chimerism rejected their kidney grafts within 11 to 29 days. Three of them, however, retained their kidney grafts permanently indicating that a transient chimerism of a few months duration may be sufficient for induction of tolerance to marrow donor organs in Cy-chimeras. The results suggest that the reversion of chimerism in Cy-chimeras may be due to different mechanisms either immunological rejection or a non-immunological substitution of the grafted marrow by the host's own hemopoiesis.

Sex-chromosome ratios in cattle and their relationship to reproductive development in freemartins

Nineteen "female" Holstein-Friesian calves born co-twin with a bull were purchased shortly after birth. One subsequently was judged to be a normal female with 0% XY (100% XX) karyotypes in cultures of blood lymphocytes. However, one typical freemartin also had 0% XY (100% XX) Karyotypes in 300 cells when examined at three ages. Overall, 18 freemartins examined at 1, 24, and 52 weeks of age averaged 60.7%, 57.9%, and 55.5% XY cells, respectively (P greater than 0.05). No systematic relationship was found between the proportion of XY cells and the abnormalities of the reproductive organs, as judged by vaginal depth and clitoral development at 1, 24, and 52 weeks, and examination of the reproductive organs per rectum at 54 weeks of age. The clitoris of untreated freemartins and those treated with estrone or estradiol postnatally did not enlarge. Testosterone treatment caused enlargement. None of the hormones affected vaginal depth. These studies provide convincing evidence that the blood lymphocyte XX:XY karyotype ratio (1) is not related to the degree of masculinization and (2) is stabile in the postnatal freemartin. Thirdly, the freemartin reproductive organs do not respond to common sex-steroid hormones postnatally other than the clitoral response to testosterone.