PubMed Health⌕ Search

Biomedical subjects

D V Cramer

Publications and source records attributed to D V Cramer.

170 records · Page 10Linked to original sources
PubMedDate not supplied

Genetic diversity within and between natural populations of Rattus norvegicus.

The levels of gene diversity for 17 polymorphic loci in natural populations of wild rats were examined for three separate locations in North and South America. The level of gene diversity in the total sample for the RT1.A locus, the dominant class I histocompatibility locus in the major histocompatibility (RT1) complex of the rat, was 0.807. The degree of gene diversity for nonalloantigenic loci scattered throughout the rat genome was 0.215, a level comparable to, if not slightly higher than, that for other mammalian species. The large and consistent levels of diversity for individuals within each population suggest that significant deviations from random mating have occurred within each group. Conclusions from analyzing genetic distance and the index of genetic differentiation between the three populations are consistent with these populations' geographic isolation and small effective population size. Assuming that the separation of the North and South American groups has existed for approximately 300 years, the effective size of these populations is estimated to be approximately 1,500 individuals. Apparent differences in the distribution of the number and frequency of alleles in the major histocompatibility complexes of mice and rats and the level of genetic differentiation among separate rat populations may be due to the effects of genetic drift in small populations.

Animals↗
PubMedDate not supplied

Carboxyfluorescein (CFSE) labelling of hepatocytes for short-term localization following intraportal transplantation.

Renewed interest in the transplantation of isolated hepatocytes into the liver as a potential therapy for liver disease has stimulated the development of methods for the identification of donor cells within the recipient organ. We describe a method for cellular tagging and in vivo identification of intraportally transplanted hepatocytes using an intracellular fluorescent dye, 5(6)-carboxyfluorescein diacetate, succinimidyl-ester (CFSE). Rat and porcine hepatocytes were isolated and labelled with CFSE. The optimal conditions for labelling consisted of a buffered saline suspension of hepatocytes (5 x 10(6) cells/mL) in 20.0 microM CFSE incubated for 15 min at 37 degrees C. In vitro, labelled hepatocytes were cultured either on fibronectin-coated chamber slides or in culture flasks. Cultures were evaluated in situ by fluorescence photomicrography or by fluorescence-activated cell sorting (FACS) after cell detachment. Cell viability was assessed serially and cultured, labelled hepatocytes retained the dye for up to 3 wk (last day of study). CFSE did not effect hepatocyte viability and there was no evidence of intercellular diffusion of the dye. In vivo, syngeneic Lewis rats underwent selective portal vein infusion of freshly isolated, labelled hepatocytes (2.0 x 10(7) cells/2.0 mL saline/animal) into the posterior liver lobes. All recipients were sacrificed 48 h and 96 h later and their livers examined. Transplanted hepatocytes were identified by fluorescence microscopy in tissue sections and by FACS following collagenase digestion of the liver tissue. CFSE persisted in a population of viable, engrafted hepatocytes. FACS analysis demonstrated that 9 +/- 3% of the hepatocytes in the posterior liver lobes were labelled 48 and 96 h after transplantation. At 96 h following transplantation, multiple engrafted hepatocytes could be observed by fluorescence microscopy around the central veins. CFSE labelling allows for both in vitro identification and in vivo localization of donor hepatocytes. Furthermore, it appears to be more stable and specific for labelling hepatocytes than other tested dyes (especially DiI).

Animals↗
PubMedDate not supplied

Lymphocytic subsets and histopathologic changes associated with the development of heart transplant arteriosclerosis.

Transplantation of vascularized organ allografts is associated with the development of arteriosclerosis in the vessels of the donor graft. We have recently examined the distribution of lymphocytic/mononuclear inflammatory cell subsets and histopathologic changes seen in the sequential development of transplant arteriosclerosis in cardiac allografts exchanged between inbred rat strain combinations (LEW-to-F344) that differ for weak histocompatibility loci. The donor grafts were harvested at 7, 14, 21, 28, 50 to 65, and 90 days after transplantation, and the vascular lesions were characterized for the immunopathologic changes associated with the chronic rejection of the grafts. The inflammatory cell infiltration of the graft myocardium was present as early as 7 days after transplantation (53.37 +/- 9.06 inflammatory cells/high-power field), and the accumulation of cells increased at 3 and 4 weeks after transplantation (112.12 +/- 16.58 and 130.40 +/- 21.24 cells/high-power field, respectively). The infiltrating inflammatory cells in the grafts at 4 weeks after transplantation were predominantly ED-1+ macrophages (63.39%), with a substantial number of OX19+ T lymphocytes (28%), OX8+ Tc/s cells (25.4%), 3.2.3+ natural killer cells (16.89%), W3/25+ Th cells (20.2%), and a small number of OX33+ B lymphocytes (1.13%) and interleukin-2 receptor+ T lymphocytes (2.6%). Among the T-cell population, most (87.6%) were positive (R73+) for T-cell receptors. The arteriosclerotic lesions present in the cardiac grafts exhibited a gradual increase in severity of the vascular intimal proliferation and a similar pattern of increased intensity of cellular infiltration. The lesions were infiltrated with inflammatory cells beginning in the first week and increasing for the first month after transplantation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Combination therapy with Brequinar sodium and cyclosporine synergistically prolongs hamster-to-rat cardia xenograft survival.

The accelerated rejection of hamster cardiac xenografts by Lewis rat recipients is due primarily to a humoral immune response. Traditional immunosuppressive agents, including cyclosporine, FK 506, and rapamycin, have not been effective in prolonging the rejection of xenografts in this model. We have recently examined the ability of the combination of cyclosporine and a new immunosuppressive agent, Brequinar sodium, to prevent the rejection of hamster xenografts. Prolongation of xenograft survival by treatment with Brequinar sodium alone (3 mg/kg/day) was minimally effective, with a median survival of 5.5 days. Conversely, a combination of Brequinar sodium (3 mg/kg/day) and cyclosporine (10 mg/kg/day), was associated with a significant prolongation of median graft survival (> 100 days). A quantitative analysis of the dose-effect relationship of Brequinar sodium and cyclosporine demonstrated a potent synergistic interaction for this combination therapy (combination index < 1). A sharp increase occurred in the binding of immunoglobulin M antibodies at day 4 after transplantation in the serum of untreated and cyclosporine-treated Lewis recipients of cardiac xenografts, whereas a clear decrease occurred in anti-hamster immunoglobulin M antibody production during this period of time in the animals treated by combined immunosuppression. Inhibition of anti-donor immunoglobulin M antibody production, as evaluated by the direct enzyme-linked immunosorbent assay and 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyltetrazolium bromide measurements, extended for more than 100 days after transplantation in the combination therapy group.(ABSTRACT TRUNCATED AT 250 WORDS)

Abdomen↗
PubMedDate not supplied

Inhibition of the pyrimidine biosynthetic pathway with S-8660, an analogue of brequinar sodium, prolongs cardiac allograft survival in rats.

The compound S-8660 is a member of a family of antiproliferative drugs that act on de novo pyrimidine synthesis through selective inhibition of the mitochondrial enzyme dihydroorotate dehydrogenase. S-8660 is highly effective in preventing the development of delayed-type hypersensitivity in mice and in suppressing human mixed-lymphocyte responses. We have tested its ability to prevent cardiac allograft rejection in the ACI (RT1a) to Lewis (RT1(1)) rat strain combination, based on the immunosuppressive activity of this compound and its similarity to another member of this group, brequinar sodium. Daily oral administration of the drug (5 to 20 mg/kg) was begun 2 days before transplantation and extended for periods of time up to 30 days after graft placement. Control grafts were promptly rejected (median survival time, 7.0 +/- 0.5 days). Administration of S-8660 was effective in extending graft survival in a dose-dependent fashion. The efficacy of S-8660 could be improved with a high initial concentration of the drug, followed by a reduction ("tapering") in the level of drug administration (median survival time, 32.0 +/- 4.6 days) or by use in combination with cyclosporine. The differences in the mode of action of S-8660, when compared to cyclosporine or FK 506, suggest that the disruption of de novo pyrimidine synthesis may be an effective and safe addition to a polytherapeutic approach for the prevention of allograft rejection in clinical transplantation.

Animals↗