Search PubMed⌕ Search

Biomedical subjects

R R Dietert

Publications and source records attributed to R R Dietert.

At least 55 records · Page 3Linked to original sources
PubMed1989

Effects of increased major histocompatibility complex dosage on chicken monocyte-macrophage function.

The influence of major histocompatibility complex (B complex) dosage on monocyte-macrophage function was examined using 4- to 6-week-old trisomic strain chickens. Di- (B15B15), tri- (B15B15B15), and tetrasomic (B15B15B15B15) progeny were produced from trisomic x trisomic crosses. Although mononuclear leukocytes from tetrasomics exhibited enhanced chemotactic activity in response to both f-met-leu-phe and Enterobacter cloacae culture supernatant as compared with that of cells from other groups, the ability to generate peritoneal exudate cells in response to intraperitoneal Sephadex stimulation was similar in all groups. Among peritoneal exudate cells, tetrasomic birds produced a significantly lower percentage of adherent macrophages with a higher proportion of Fc receptor-positive and CMTD-2-reactive macrophages than either disomic or trisomic chickens. Both tetrasomic and trisomic peritoneal macrophages exhibited a reduced phagocytic activity for unopsonized but not opsonized SRBC than was found with disomic macrophages. Thus, the number of major histocompatibility complex copies present in cells appears to influence monocyte-macrophage function.

Aneuploidy↗
PubMed1989

Monocyte function in chickens with hereditary muscular dystrophy.

Monocyte functions of Storrs strain muscular dystrophic (MD) chickens and Storrs control strain were compared. After short-term in vitro culture of monocytes, cells taken from Storrs MD chickens had a significantly lower incidence of cells capable of phagocytizing sheep red blood cells than did cells cultured from the control strain. In contrast, no difference was found in the ability of MD vs. control strain blood mononuclear cells to undergo in vitro chemotaxis in response to a bacterial culture supernatant. The study also revealed a distinct peripheral blood leukocyte profile of young MD chickens: elevated percentages and absolute numbers of granulocytes. The total leukocyte count in MD chickens was not significantly different from that of normal chickens. These findings extend previous observations concerning altered reticuloendothelial system function in MD strain chickens.

Animals↗
PubMed1988

MHC-chromosome dosage effects: evidence for increased expression of Ia glycoprotein and alteration of B cell subpopulations in neonatal aneuploid chickens.

Quantitative variation in the expression of MHC-encoded class II (Ia) glycoproteins has been associated with stages of lymphocyte development and a number of disease conditions. We have used an avian MHC dosage model to study the regulation of Ia expression and the effects of quantitative variation in membrane Ia on B-cell development. Lymphocyte membrane expression of Ia glycoprotein molecules and the frequency of small-versus-large lymphocytes were examined in trisomic line chickens containing either two (disomic), three (trisomic), or four (tetrasomic) copies of the microchromosome encoding the MHC. This was accomplished by quantitative laser flow cytometry analysis of bursa-resident B lymphocytes from neonatal trisomic line chickens. The aneuploids (trisomics and tetrasomics) expressed more cell surface Ia than did normal disomic birds. Furthermore, the aneuploids exhibited a greater frequency of small B lymphocytes as compared to disomic chickens. Dual parameter analysis of Ia quantity and cell size was undertaken to study B lymphocyte subpopulations in these birds. It was observed that the aneuploids had altered frequencies of two distinct subpopulations of cells: (1) an increased percentage of small cells which express high levels of Ia antigen and (2) a decreased percentage of large cells which express medium levels of Ia antigen. These findings support the view that MHC class II genes are regulated and expressed in a dosage-dependent manner. Therefore, increases in the number of MHC copies per cell result in the increased expression of Ia glycoprotein on bursa-resident B cells. The stepwise increase in membrane Ia on trisomic and tetrasomic B cells is correlated, and perhaps casually linked, with progressive degrees of alteration of developing B cell subpopulations in the bursa of aneuploid chicks. These events may ultimately alter the humoral immunity of the aneuploid animals.

Aneuploidy↗
PubMed1988

The chicken macrophage response to carbohydrate-based irritants: temporal changes in peritoneal cell populations.

Temporal changes in the recruitment and functional activation of Cornell K strain chicken peritoneal macrophages elicited by starch and dextrans were determined. During a 72-hr period following intraperitoneal injection, Sephadex (cross-linked dextran) elicited a gradually increasing number of peritoneal exudate cells (PECs) which contained greater than or equal to 78% macrophages in the adherent cell population. In contrast, starch tended to elicit higher numbers of PECs early in the stimulation process, with heterophils comprising a major proportion of the adherent cells. Later in the time course, macrophages were the predominant adherent cell type. Comparisons of PEC recruitment using Sephadex vs. low molecular weight dextrans demonstrated that the low-molecular weight dextrans elicited fewer PECs than did Sephadex; unlike Sephadex, however, the low molecular weight dextrans generated a significant peak of heterophil infiltration that was similar, although delayed, to that produced with starch. Sephadex-stimulated peritoneal macrophages exhibited time-dependent functional acquisitions for 1) the phagocytosis of sheep erythrocytes, 2) the engulfment of opsonized sheep erythrocytes, and 3) opsonin-erythrocyte rosetting. Acquisition of phagocytic activity for uncoated vs. opsonized erythrocytes occurred under very different rates during the time course. The results suggest that both the nature of the irritant and the time point of cell harvest can be appropriately selected to provide the particular cell population and functional status desired for subsequent in vitro analyses.

Animals↗
PubMed1988

Chemotactic activity of chicken blood mononuclear leukocytes from 15I5-B-congenic lines to bacterially-derived chemoattractants.

The chemotactic activity of chicken blood mononuclear leukocytes was examined in partially-developed 15I5-B-congenic chicken lines using Enterobacter cloacae culture supernatant and formyl-methionyl-leucyl-phenylanine (f-met-leu-phe) (10(-5)M). Cells from seven different coded B-congenic lines were used to study each chemoattractant in vitro. Mononuclear cells from lines .15I-B5,.C-B12 and the background line 15I5 (B15) exhibited a significantly greater directed migration to bacterial supernatant than did cells from four lines carrying the B2, B2, B13, and B19 haplotypes, respectively. Similarly response to f-met-leu-phe was greatest in lines .15I-B5,.C-B12 and .N-B21, with the same four lines exhibiting a significantly lower response. Since f-met-leu-phe was originally isolated from bacteria, the results indicate that these lines possess differential chemotactic responses to certain bacterially-derived chemoattractants. Major histocompatibility complex (MHC) differences between the lines may serve as a genetic basis for the differential responses. Extrapolation of these results to other chemotactic-receptor systems would require further examination.

Animals↗
PubMed1988

Tissue-specific accumulation of metallothionein in chickens as influenced by the route of zinc administration.

The effect of the route of zinc (Zn) administration on the induction of metallothionein (MT) in various tissues of chicks was examined. Four-week-old, male chicks were assigned to one of four treatments: 5 mg Zn/kg intraperitoneal (i.p.) injection, 5 mg Zn/kg intravenous (i.v.) injection, 16 mg Zn oral (O) dose or a saline control (C). Chicks were fasted overnight, treated and killed 24 h later. 109Cd radioassay analysis of liver (L), kidney (K) and pancreas (P) showed a significant elevation of MT in all tissues except K of i.v. chicks. Comparing tissue MT accumulation within treatments showed that L was induced to a greater extent than P for the i.p. treatment (P/L ratio = 0.69 +/- 0.04), while the reverse effect was seen for both O (1.51 +/- 0.10) and i.v. (1.67 +/- 0.14) chicks, reflecting greater P than L accumulation. Zn injected i.p. did not result in significantly greater total peritoneal exudate cell (PEC) or macrophage (M) numbers than saline-injected controls. Sephadex, while causing massive increases in PEC and M, did not induce tissue MT, demonstrating the lack of correlation between PECs or Ms and MT accumulation. Feed intake by chicks during the 24-h period following i.p. Zn treatment was only 30% of that by controls. A subsequent experiment demonstrated that a similar restriction in feed intake increased L but not P MT. This increase accounted for 17.8% of the L induction due to i.p. Zn injection. This does not fully account for the reduction in P/L that is characteristic of i.p. treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1987

Targeting of chemical mutagens to differentiating B-lymphocytes in vivo: detection by direct DNA labeling and sister chromatid exchange induction.

In vivo systems for analyzing mutagen interactions with a specific differentiating cell population are rare. Taking advantage of the unique anatomical features of the bursa of Fabricius in the chicken, we explored the possibility of targeting chemical mutagens to a defined differentiating cell population in the animal, namely, the B-lymphocytes series. Such cells are known to be the targets for the oncogene-activating avian leukosis virus. Targeting of chemicals to cells of the bursa was demonstrated by application of the DNA-specific fluorochrome 4'-6-diamidino-2-phenylindole (DAPI) to the anal lips of neonatal chicks. Bright nuclear fluorescence of cells in the bursa was demonstrated to occur within minutes after the application of 500 microliters of DAPI. DAPI labeling of nuclei was detected up to several days after a single application. No nuclear labeling was exhibited in cells of neighboring tissues. Methyl methanesulfonate (MMS) (10 microliters) was applied to the anal lips of day-old chicks to study dose-response kinetics for mutagen targeting to DNA of dividing B-lymphocytes in the bursa. Since the mitotic index was found to be quite high (25-30%) in the bursa, chromosome analysis was used to assay for genome damage. Sister chromatid exchange frequencies of 3.9, 7.3, and 9.0 (baseline 2.5) per cell were obtained at MMS dosages per animal of 50 micrograms, 100 micrograms, and 200 micrograms respectively. These indicate the rapid and quantitative localization of DNA-binding chemicals to cells of the bursa, particularly the resident B-lymphocytes. The bursa should be a useful system for studying mutagen-DNA interactions in the differentiating B-lymphocyte and subsequent influences on the development of immunity and lymphoproliferative disease.

Animals↗
PubMed1987

Cellular expression of MHC glycoproteins on erythrocytes from normal and aneuploid chickens.

The major histocompatibility complex (MHC) in the chicken (B-complex) encodes glycoproteins homologous in function and distribution to the mammalian MHC. These are the B-F (class I) and B-L (class II) glycoproteins. In addition, a third glycoprotein (B-G) is also encoded by the chicken MHC. We are interested in examining gene regulation and cellular expression of these MHC gene products in the chicken. The trisomic line of chickens is being developed as an animal model for this purpose. Birds from this line contain either 2, 3, or 4 MHC-encoding chromosomes. In this study, we investigated the hypothesis that the quantities of B-complex glycoproteins on the membranes of fully differentiated erythrocytes are proportional to the number of MHC-encoding chromosomes present in particular birds. Hemagglutination final titer and quantitative adsorption assays were carried out using erythrocytes from disomic and aneuploid chickens homozygous for the B15 haplotype. The average hemagglutination final titers were higher for tetrasomic cells as compared to disomic cells. Furthermore, in adsorption assays, employing a B15 cross-reacting alloantiserum, trisomic and tetrasomic erythrocytes displayed increased adsorption capabilities (1.6 and 3.1 fold, respectively) compared to disomic control cells. These results indicate a step-wise increase in the amounts of erythrocyte surface glycoproteins per cell in the trisomics and tetrasomics, respectively. Such findings are consistent with a MHC-dosage-dependent model of gene expression in homeothermic vertebrates.

Adsorption↗
PubMed1987

Chromosomal localization of the major histocompatibility (B) complex (MHC) and its expression in chickens aneuploid for the major histocompatibility complex/ribosomal deoxyribonucleic acid microchromosome.

By the cytogenetic method of trisomy mapping, the major histocompatibility complex (MHC) (B) was located on the microchromosome that also contains all of the ribosomal ribonucleic acid (rDNA) genes that are detected as a nucleolar organizer region. Crosses involving aneuploid chickens homozygous or heterozygous for particular B haplotypes yield an F1 of disomic, trisomic, and tetrasomic offspring suitable for studies of gene dosage effects and gene regulation. Studies to date show that MHC genes are expressed on each chromosome in aneuploid cells unlike the rDNA gene cluster, which is regulated to produce only diploid levels of mature rRNA. Biological effects of extra MHC chromosome dosage range from altered cell surface content of glycoproteins to altered growth potential of chickens. In addition, enhanced MHC-encoded cell surface products may influence the progression of B-cell differentiation and cell population dynamics in the developing bursa of Fabricius. Recent research shows a possible mechanism to account for the formation of unequal products in meiosis within the rDNA and MHC gene clusters. Unequal recombinational events may be promoted in the meiotic process in trisomic chickens.

Aneuploidy↗
PubMed1986

Induced autoantibodies to fetal erythroid antigens in the chicken.

Cornell Obese (OS) (B13B13), Special C (Sp.C) (B13B13) and K-strain White Leghorn chickens (B15B15) were examined for both naturally occurring and induced autoantibodies directed against erythroid fetal antigens. Obese chickens have been reported to produce high levels of autoantibodies to thyroglobulin and to occasionally produce antinuclear autoantibodies specific for erythrocytes. Despite producing high levels of antithyroglobulin autoantibodies and antibodies cross-reactive with erythrocytes, no OS chickens were found to possess naturally occurring autoantibodies to fetal-specific antigens on erythrocytes. However, such antibodies were induced following immunization with fetal erythrocytes derived from a strain allogeneic for the major histocompatibility complex (MHC), the B-complex. Challenge with both intact erythrocytes and erythroid membranes in Freund's complete adjuvant resulted in production of antibodies specific for fetal antigens. The ability to induce autoantibodies to fetal erythrocytes was not restricted to the OS-strain; similar antibodies were detected in the Cornell K-strain and Special C-strain chickens even when intrastrain immunizations were employed. These results suggest that antibodies can be induced to fetal antigens on chicken erythrocytes in both autoimmune and normal chickens given the appropriate antigen presentation.

Animals↗
PubMed1986

Genetic variation in the recruitment and activation of chicken peritoneal macrophages.

Genetic variation in the ability to recruit and activate peritoneal macrophages was examined in seven partially developed 15I5-B congenic White Leghorn chicken lines. While the ability to generate peritoneal exudate cells (PECs) was similar in all lines, major differences were observed in the numbers, composition, and functional activity of harvestable peritoneal adherent cell populations. In response to a general stimulant, Sephadex, lines .7-2 and .6-2 produced the greatest numbers of adherent peritoneal cells while lines .C-12 and .15I-5 were among the poorest responders. Macrophage percentage of adherent PECs varied between lines. 15I5 chickens produced a consistently high percentage of adherent macrophages while .6-2 birds exhibited the lowest macrophage percentage at all ages examined. Phagocytosis was used as one measure of the level of macrophage activation and similar results were obtained using both opsonized and unopsonized sheep erythrocytes; adherent peritoneal cells from lines .6-2, .7-2, and .P-13 exhibited the highest activity and .C-12, .15I-5, and background 15I5(B15) lines produced cells with the lowest phagocytic activity. In a second functional assay, the killing of Salmonella typhimurium, macrophage-rich cells from line .P-13 exhibited the lowest activity which was significantly lower than that obtained with cells from lines .6-2 and .15I-5. Antigen-specific stimulation of peritoneal adherent cells by ferritin also showed that .C-12 was a low responder in contrast with other lines. The results indicate that these genetic lines differ in peritoneal macrophage function and suggest that the chicken major histocompatibility complex may influence certain properties of chicken macrophage function.

Animals↗
PubMed1986

Effect of selenium and vitamin E dietary deficiencies on chick lymphoid organ development.

Diets specifically deficient in selenium (Se) and/or vitamin E or adequate in both nutrients were fed to chicks from the time of hatching. Lymphoid organs (bursa, thymus, and in some instances, spleen) were collected from chicks 7-35 days of age. Growth of the chicks fed these diets was monitored over the experimental period as was lymphoid organ growth. The development of the primary lymphoid organs was further assessed by histological techniques and the organ contents of vitamin E (alpha-tocopherol) and Se were determined. Specific deficiencies of either Se or vitamin E were found to significantly impair bursal growth as did a combined deficiency. Thymic growth was impaired only by the combined deficiency diet. Severe histopathological changes in the bursa resulted from the combined deficiency and these were detectable by 10-14 days after hatching. These changes were characterized by a gradual degeneration of the epithelium and an accompanying depletion of lymphocytes. Similar changes, although slower to develop and less severe, were observed in the thymus as a result of the combined deficiency. When both serum and tissue levels of vitamin E and Se were monitored, it was observed that these were rapidly and independently depleted by the specific deficiency diets. These data suggest that the primary lymphoid organs are major targets of Se and vitamin E dietary deficiencies and provide a possible mechanism by which immune function may be impaired.

Animals↗
PubMed1986

Monoclonal antibodies reactive with chicken peritoneal macrophages: identification of macrophage heterogeneity.

Mouse monoclonal antibodies (MCAs) were prepared against chicken inflammatory macrophages for the purpose of analyzing macrophage heterogeneity. Macrophage-rich adherent peritoneal exudate cells harvested from Cornell K-strain chickens 42 hr after stimulation with Sephadex were used as immunogens in the production of the monoclonal antibodies. Eight hybridoma clones producing antibodies reactive with chicken peritoneal macrophages were subjected to characterization. While six of the monoclonal antibodies cross-reacted with various hematopoietic cell types, two MCAs (CMTD-1 and -2) were restricted in reactivity to macrophages. CMTD-1 was found to react with activated peritoneal macrophages generated by several irritants. In contrast, CMTD-2 identified a subpopulation of macrophages elicited by specific carbohydrate-based stimulants. This presumably was based on the cross-reaction of this MCA with specific carbohydrate linkages. Analysis using flow cytometry revealed the time-dependent appearance of CMTD-2-positive peritoneal macrophages between 24 and 52 hr after ip Sephadex injection. This subpopulation of peritoneal macrophages was found to be heterogeneous for the ability to undergo in vitro phagocytosis of sheep erythrocytes. CMTD-2-positive cells were also detected in the thyroids of 2-week-old Obese strain chickens with spontaneous autoimmune thyroiditis and at a low incidence in the spleens of normal chickens.

Animals↗
PubMed1985

Embryonic exposure to aflatoxin-B1: mutagenicity and influence on development and immunity.

Chick embryos were mutagenized in ovo in order to study developmentally related alterations in immune functions in survivors of this prenatal toxicant insult. In this experimental system, a single exposure of 6-day chick embryos to 0.1 microgram aflatoxin-B1 (AF-B1) in 10 microliters of acetone was employed, and the control embryos received 10 microliters of solvent alone. This dosage of AF-B1 administered to 6-day embryos was found to increase the incidence of sister chromatid exchanges in blood cells approximately fivefold above the baseline observed in solvent controls. A second sham control, where no solvent was administered, was included in some experiments. The cell cycle times in blood increased slightly during the initial exposure to AF-B1. However, a majority of the AF-B1 and acetone exposed embryos survived and hatched without incident. Losses occurred mainly in the latter part of embryogenesis. After hatching, no significant differences were observed in body weight between different treatment groups up to 26 weeks of age and no change in primary humoral immunity was detected. In contrast, two parameters of cell-mediated immunity, graft vs host (GvH), and cutaneous basophil hypersensitivity (CBH) reactions were both depressed as a result of exposure to AF-B1. The AF-B1 treatment group was significantly reduced in the GvH reaction compared with sham-treated controls. In the CBH assay, AF-B1-exposed chicks showed reduced immunity compared with acetone controls. These results suggest that long-term selective immune depression can occur following embryonic exposure to AF-B1.

Aflatoxin B1↗