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Biomedical subjects

R B Ashman

Publications and source records attributed to R B Ashman.

At least 109 records · Page 6Linked to original sources
PubMed1985

Mouse serum as a medium supplement for murine immune responses in vitro.

In vitro generation of secondary anti-viral H-2 restricted cytotoxic T cells (Tc cells) alloreactive Tc cells, alloantigen-induced T cell proliferation, bacterial lipopolysaccharide (LPS)-induced B cell proliferation and anti-dinitrophenyl IgM and IgG antibody responses were used to evaluate pools of mouse sera (MS) and other animal sera as medium supplements by comparison with 5-10% fetal calf serum (FCS). Some batches of normal MS were comparable with FCS while others inhibited Tc cell responses when used at 1%, particularly with limiting stimulator cell numbers. In contrast, 2 pools of nude mouse sera and several pools of MS from thioglycollate-injected mice (TMS) used at 1% were consistently comparable with FCS at 5-10% in terms of in vitro generation of effector Tc cells and antibody secreting B cells. TMS at 1% was satisfactory for Tc cell responses either fresh, after heat inactivation at 56 degrees C for 30 min, or after storage for 6 months at -70 degrees C. 0.5% or 2% heat-inactivated rat and rabbit sera (but not guinea pig sera) were also satisfactory for Tc cell generation. Total thymidine incorporation into proliferating B or T cells was 5-15-fold lower in cultures with 1% normal MS, nude MS or TMS than with 5% FCS, but stimulation indices with 1% nude MS and TMS were similar to those with 5% FCS, whereas 1% normal MS apparently completely inhibited stimulation. One percent syngeneic TMS is a convenient, reliable alternative to 5-10% FCS in culture medium, supporting all the murine responses listed above.

Animals↗
PubMed1985

The influence of graft size on the induction of immunity versus tolerance to H-Y in H-2k strains of mice.

Unprimed female CBA mice do not reject large (10 mm2) syngeneic male skin grafts. However, a high proportion do reject small (4 mm2) grafts. Nevertheless, rejection does not invariably result in an anamnestic response. In some cases, the immunity induced by the rejection of a small graft was overcome, and tolerance was induced by a subsequent challenge with a large graft. This suggests that the transplantation response to minor antigens is subject to active regulation, and screening of other H-2k strains indicates that the nature of the response (i.e., immunity or tolerance) is determined by a gene or genes mapping outside the major histocompatibility complex.

Animals↗
PubMed1985

The mechanical properties of immature osteopetrotic bone.

The elastic properties of the longer bones of the fore and hind limbs of an osteopetrotic Angus calf were measured using an ultrasonic technique. The same bones of a second Angus calf with unaffected bone tissue were also studied. The osteopetrotic bones were found to exhibit statistically significant lower values of density and mineral content than did the unaffected bones (P = .0054 and P = .0492, respectively). This result is contrary to what has been reported in the literature. The variations of the elastic properties and the density around the circumference of both the immature osteopetrotic femur and the unaffected femur were found to be similar to those previously measured on normal adult bovine femora.

Animals↗
PubMed1985

The bone tissue of the canine mandible is elastically isotropic.

This paper reports experimental measurements which show that canine mandibular bone tissue is elastically isotropic. Earlier work has established that human, canine and bovine cortical bone tissue of the femur, tibia and skull are elastically anisotropic and therefore the reported isotropy of mandibular tissue was unexpected. The isotropic elastic moduli of the canine mandible are represented by a Young's modulus of 7.5 GPa and a Poisson's ratio of 0.4. Earlier work gave the three orthotropic Young's moduli of the cortical one of the canine femur as 12.8 GPa, 15.6 GPa and 20.1 GPa. The experimental technique employed is elastic wave propagation at ultrasonic frequencies.

Animals↗
PubMed1985

Immunosuppressive effects of cationic vesicles.

Double chained cationic amphiphiles closely related to those in widespread household and commercial use have been shown to inhibit the generation of cytoxic T lymphocytes in mixed lymphocyte reactions in vitro, and to inhibit inflammatory responses caused by the injection of alloreactive cytotoxic lymphocytes into the footpads of mice. The immunosuppressive effects are not due to non-specific toxicity, but are probably due to inactivation or deletion of cytotoxic T cell precursors in the in vitro experiments, and modification of the inflammation induced by activated T cells in vivo. Apart from the cautionary aspects in relation to public health, the results offer a new approach to immunology and cell biology in terms of modification of cell membranes, and a rationale for the systematic design of a class of immunosuppressive drugs.

Animals↗
PubMed1985

The cytotoxic response to murine cytomegalovirus. III. Lymphokine release and cytotoxicity are dependent upon phenotypically similar immune cell populations.

Murine cytomegalovirus (MCMV)-immune lymph node (LN) cells were generated following 4 days culture of draining popliteal LN cells removed after bilateral hind footpad inoculation of mice with 4 X 10(2) p.f.u. MCMV. This cell population expressed both cytotoxic activity against MCMV-infected mouse embryo fibroblasts (MEF) and the capacity to release lymphokine upon stimulation with MCMV-infected MEF. Cytotoxicity and lymphokine release were Class I, H-2-restricted, virus-specific and dependent upon Thy1. 2+, Lyt2+ cells. Mixing of 5 X 10(5) MCMV-immune T cells with an excess of syngeneic MCMV-infected MEF stimulators produced detectable levels of the lymphokine interleukin-3 by 1 h, with a maximum rate of its release between 1 and 6 h and plateau levels by 14 h. The capacity to stimulate virus-specific MCMV-immune T cells was acquired by MEF at 1 h after MCMV infection with maximum stimulator ability attained by 8 h. In the presence of a fixed number of MCMV-immune T cells, and titration to excess of syngeneic 3 h or 18 h MCMV-infected MEF, lower interleukin-3 plateau levels were obtained with 3 h than with 18 h MCMV-infected stimulators. This suggested that fewer T cells responded to 3 h than to 18 h MCMV-infected MEF.

Animals↗
PubMed1985

The cytotoxic response to murine cytomegalovirus. I. Parameters in vivo.

Combined in vivo and in vitro protocols for the generation of anti-murine cytomegalovirus (anti-MCMV) cytotoxic responses were investigated using BALB/c mice and syngeneic mouse embryo fibroblast target cells. Injections of doses of MCMV from 10(2.6) up to 10(6.1) p.f.u. into the hind footpad, harvest of draining popliteal lymph node cells after 6 to 8 days, followed by 4 days culture of these cells gave similar and optimal cytotoxic activity against MCMV-infected target cells. After injection of 10(4.6) p.f.u. into the hind footpad, MCMV was detectable at about 10(3) to 10(4) p.f.u. per popliteal node after 3 days, but became undetectable in most animals by 6 days. Cell numbers in the draining popliteal lymph node increased following MCMV inoculation into the hind footpad, but the extent of the increase was inversely related to virus dose and bore no relationship to the anti-MCMV cytotoxic potential of the cells. Lymph node cells applied directly to target cells upon harvest from MCMV-infected mice never gave detectable anti-MCMV cytotoxic activity at 2, 4, 6, 8, 10, 12, 17 or 19 days post-infection, but lysis of uninfected syngeneic targets was obtained 4 to 8 days post-infection.

Animals↗
PubMed1985

The cytotoxic response to murine cytomegalovirus. II. In vitro requirements for generation of cytotoxic T cells.

A cytotoxic response to murine cytomegalovirus (MCMV) was obtained by the culture of lymph node cells from mice inoculated with MCMV into both hind footpads 7 days previously. The cytotoxicity was mediated by Thy1.2+, Lyt2+, H-2-restricted effector cells and was virus-specific. Investigation of the in vitro conditions established that T cell proliferation was necessary for optimal generation of cytotoxicity, that proliferation was dependent upon Thy1.2+, Lyt2+ cell populations and that supernatants from concanavalin A-activated spleen cells enhanced the levels of cytotoxicity obtained.

Animals↗
PubMed1984

A continuous wave technique for the measurement of the elastic properties of cortical bone.

A continuous wave technique is described for measuring the nine independent orthotropic elastic coefficients from a single cubic specimen. The side dimensions of this cubic specimen are on the order of 5 mm. Because of the small size of the specimen, the spatial resolution of material inhomogeneity using this technique is quite good. Although it is possible to apply this technique to any elastic material such as woods or metals, the elastic properties of human and canine cortical femora are presented here. The orthotropic elastic coefficients and the variation of these coefficients are presented as a function of anatomical position.

Animals↗
PubMed1984

Alloreactive cytotoxic T lymphocytes lyse syngeneic influenza-infected tumour cell targets.

Spleen cells from C57BL/10(H-2b) mice, when stimulated in vitro to Kk alloantigens, lysed syngeneic influenza A virus-infected tumour cell targets but not uninfected or vaccinia- or Sendai virus-infected targets. Peritoneal macrophage targets infected with influenza virus were not lysed. Lysis of H-2k targets and EL4-A influenza virus-infected targets was abrogated by treatment of effectors with anti-Thy 1.2 plus C and anti-Lyt 2 plus C but not by anti-Lyt 1 plus C or anti-GM-1, a natural killer cell-specific, monoclonal antibody plus C. Cold target inhibition experiments indicated that one and the same population of Tc cells see H-2Kk and H-2b plus influenza virus. Sensitization of C57BL/10 mice to Kk in vivo did not potentiate virus clearance from lungs. The data are discussed in relation to observed Ir gene effects and variation and modulation of H-2 antigens on tumour cells.

Animals↗
PubMed1984

Variation in H-2 antigen expression on lymphomyeloid cells in semi-allogeneic irradiation chimeras.

Spleen cells from 30 individual murine irradiation chimeras of the type (P1 X P2)F1----P1 were compared in a rosetting assay for H-2K and H-2D cell surface antigen expression with normal (P1 X P2)F1 hybrid controls. Eleven out of the 30 chimeras were in the normal range, but the other 19 differed from F1 controls by 4- to 100-fold in endpoint titre for at least one H-2K or H-2D antigen. Every possible class of variation was found, i.e. up or down variation of H-2K or H-2D antigens of P1 or P2 type. This evidence, together with data from T6 chromosome marker experiments which also showed full reconstitution of lethally irradiated P1 recipients by (P1 X P2)F1 donor lymphomyeloid stem cells, suggested that incomplete reconstitution was not the cause of H-2 antigenic variation. Low expression of P2 H-2 antigens on spleen cells derived from (P1 X P2)F1----P1 chimeras was investigated further. Fifteen lethally irradiated (P1 X P2)F1 recipients of bone marrow cells from two such chimeras were all of normal F1 H-2 phenotype when tested 10-12 weeks after reconstitution, thus excluding stable, low P2 H-2-expressing variant F1 stem cells as a cause of the phenomenon. If P1 recipients were hyperimmunized against P2 cells before lethal irradiation and reconstitution with (P1 X P2)F1 stem cells, there were significantly fewer Till- McCulloch colonies in their spleens 10 days after reconstitution than in spleens of unimmunized controls. Also greater than 90% of immunized recipients died by 6 weeks after stem cell injection but two survivors both showed very low levels of P2 H-2K and H-2D antigens. These results together with previously published evidence of anti-P2 Tc cell activity and P2 skin graft rejection in (P1 X P2)F1----P1 chimeras suggested that residual anti-P2 immunological capability in lethally irradiated P1 recipients may be associated with low P2 H-2 expression on their F1-derived spleen cells, although the mechanism does not involve selection of stable, variant F1 stem cells. The mechanism(s) of other classes of variation in H-2 expression in (P1 X P2)F1----P1 chimeras were not investigated.

Animals↗
PubMed1983

Primary immune responses to H-Y in BALB/c-H-2k mice.

Female mice of the H-2k haplotype have been thought not to reject primary grafts of male skin. However, most BALB/c-H-2k female mice bred in our colony rejected syngeneic male grafts. Graft rejection was sufficient to prime the mice for the subsequent generation of H-Y-specific cytotoxic T cells and delayed-type hypersensitivity responses.

Animals↗
PubMed1983

Induction of T cell hyporesponsiveness to Bebaru in mice, and abnormalities in the immune responses of progeny of hyporesponsive males.

Non-specific hyporesponsiveness of cytotoxic T cells to alphaviruses and alloantigens was induced in male mice by multiple, large injections, starting at birth, of gamma-inactivated alphavirus, stock-grown in outbred mouse brains. Offspring of matings between 2 out of 17 treated males and normal females also exhibited significant non-specific hyporesponsiveness (in comparison with normal control mice), without prior exposure to gamma-inactivated alphavirus stock.

Alphavirus↗