Biomedical subjects

J F Maddox

Publications and source records attributed to J F Maddox.

70 records · Page 4Linked to original sources

PubMed1991

Increased 12-HETE production in bovine lymphocytes during selenium deficiency.

When peripheral blood lymphocytes were incubated with arachidonic acid in the presence of Ca++ ionophore (A23187), the cells from the selenium-deficient dairy cows produced significantly greater quantities of 12-hydroxyeicosatetraenoic acid (12-HETE) than the cells from the selenium-supplemented animals. The major product of reaction was verified as 12-HETE by cochromatography with a 12-HETE standard on an HPLC and structural analysis by GC-MS. Additionally, concanavalin A-stimulated lymphocyte proliferation was significantly decreased in cells from the Se-deficient cows. Furthermore, 12-HETE generated by the A23187-stimulated lymphocytes inhibited lymphocyte proliferation when added to Se-supplemented cell cultures. These observations suggest that self-regulation of lymphocyte proliferation might be mediated by 12-HETE production, especially during an altered nutritional state such as Se deficiency.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗

PubMed1991

The nucleotide sequence and evolution of ovine MHC class II B genes: DQB and DRB.

The nucleotide sequences of one Ovar-DQB gene, excluding exon 1 and parts of the introns, and one Ovar-DRB pseudogene are presented. The structure of the Ovar-DQB gene is typical of a major histocompatibility complex (MHC) class II B gene and demonstrates considerable sequence similarity with that of humans including such characteristics as the less common polyadenylation signal, ATTAAA. The ovine sequence has a typical 5' acceptor splice signal for exon 5, thus potentially encoding a full length cytoplasmic tail. The Ovar-DRB gene identified in this study was found to be a pseudogene, lacking a defined exon 2 and containing premature termination codons in both exons 3 and 4. The 3' donor splice site of exon 3 is also atypical. A purine-pyrimidine microsatellite repeat, (dC.dA)15, in the 3' region of the pseudogene may be a hotspot for recombination within the ovine DR subregion.

Amino Acid Sequence↗

PubMed1991

Dietary selenium effects on milk eicosanoid concentration in dairy cows during coliform mastitis.

The effect of selenium deficiency on the product profile of arachidonic acid oxidation by enzymatic pathways in Holstein cows with experimentally-induced coliform mastitis was investigated. The animals were fed dairy rations containing 0.05 mg Se/kg dry matter, with the supplemented group receiving additional Se to increase the dietary concentration to approximately 0.35 mg Se/kg dry matter. Cows were inoculated intracisternally with 30 colony-forming-units of Escherichia coli at 14-16 weeks of lactation. Eicosanoids and bacteria numbers were recorded at various intervals of time for 60 h postinoculation. Milk from cows fed the Se-depleted diet had significantly higher (p less than 0.05) concentrations of TXB2 between 24 and 48 h and 6-keto-PGF1 alpha between 24 and 60 h postinoculation. Milk PGE2 concentration was significantly higher in the Se-deficient group at 24 h, whereas LTB4 was higher between 36 and 60 h postinoculation in the Se-deficient cows (p less than 0.05). Milk bacteria numbers were significantly higher between 16 and 24 h postinoculation in the Se-deficient group and three of the four cows in this group required euthanasia, whereas all four cows in the Se-supplemented group recovered without therapeutic intervention. These data indicate marked effects of dietary Se on milk eicosanoid concentrations in response to an E. coli infection. The changes in eicosanoid concentrations may be associated with the altered pathogenesis and outcome of mastitis in a Se-deficient state.

6-Ketoprostaglandin F1 alpha↗

PubMed1988

Characterization of a 95,000 molecule on sheep leucocytes homologous to murine Pgp-1 and human CD44.

The phagocyte glycoprotein-1 (Pgp-1) antigen of mice is a 94,000 MW molecule with a wide tissue distribution, but no attributed function. We produced a monoclonal antibody (mAb) termed 25-32 which recognizes the Pgp-1 molecule of numerous mammalian species, including humans and sheep. Preclearing experiments with I42/5, a rat anti-mouse Pgp-1 mAb that cross-reacts with human Pgp-1, established the specificity of 25-32 for human and sheep Pgp-1. Moreover, an antibody recognizing human CD44, termed F10-44-2, also reacted with the same molecule as that recognized by 25-32 and I42/5, so establishing the co-identity of CD44 and Pgp-1. Within the sheep thymus, Pgp-1 was expressed most strongly by medullary thymocytes and stromal cells, and by small numbers of cells at the subcapsular cortex. Pgp-1 was expressed early in thymic ontogeny; all 35-40-day gestation fetal sheep thymocytes were intensely Pgp-1+, but by 80 days the number of reactive thymocytes had decreased to adult levels. The expression of Pgp-1 on lymphocytes was markedly increased after stimulation with mitogens, or with phorbol esters and ionomycin. The highly conserved nature of Pgp-1 through evolution, its expression on virtually all cell types within the body, and its increased expression on rapidly dividing cells indicate that this molecule mediates an important function, possibly serving as a hormone or metabolite receptor.

Animals↗

PubMed1987

A monoclonal antibody to the p220 component of sheep LCA identifies B cells and a unique lymphocyte subset.

The leukocyte common antigen (LCA, CD45) of humans and rodents is expressed exclusively by leukocytes, and has been implicated in a number of immune functions (1-4), although its precise function is still unknown. Three monoclonal antibodies (mAbs) were produced which identified different epitopes on the LCA of sheep. mAbs 1-11-32 and 38-42 reacted with determinants of LCA expressed on all leukocytes, but showed differential reactivity with thymocytes. Another antibody, 20-96, identified an epitope of LCA expressed mainly on B cells, but also on a unique lymphocyte subset contained mostly in peripheral blood, which was 20-96high, sIg-, CD4-, CD8-, SBU-T19-, but CD5+. These cells constituted only 5-6% of PBL. The cellular lineage of this latter subset is uncertain since these cells appeared to be unrelated to B cells, and were absent from the thymus. Unlike the other two mAbs to LCA, 20-96 was not reactive with macrophages and granulocytes. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of material immunoprecipitated by the "pan" LCA-specific mAbs revealed lymphocyte forms with molecular weights (MW) of 220, 210, and 190K, whereas 20-96 immunoprecipitated only a 220K MW form. The expression and MW of LCA on thymocytes or ileal Peyer's patch (IPP) cells differed from those on peripheral lymphocytes. B cells in IPP, which constitute 98% of cells, expressed the 20-96 determinant at low density, in contrast to its high expression on peripheral B cells. LCA from IPP existed in two forms of 220 and 190K MW, whereas LCA from peripheral B cells was entirely 220K MW, and thymus 210 and 190K MW.

Animals↗

PubMed1987

Lymphocyte antigens of sheep: identification and characterization using a panel of monoclonal antibodies.

A panel of monoclonal antibodies has been developed and used to identify and characterize the lymphocyte antigens of sheep. These studies have shown that sheep lymphocyte antigens display similar, if not identical, tissue distributions to their analogues in other species. Some of the major sheep antigens, including CD5, CD4, CD8, SBU-T19, Pgp-1, LCA and the MHC antigens, are described in detail.

Animals↗

PubMed1987

Ontogeny of ovine lymphocytes. II. An immunohistological study on the development of T lymphocytes in the sheep fetal spleen.

The development of T and B lymphocytes in the ovine fetal spleen was studied immunohistologically using a panel of monoclonal antibodies. A specific sequence of appearance of lymphocyte markers on cells was observed. At 43-44 days of gestation, SBU-T1- and SBU-T8-positive lymphocytes were present in low numbers. However, no SBU-T4, 20.96-, 25.69-, 38.38-, or 46.66-positive lymphocytes were seen until 50-55 days of gestation. Surface immunoglobulin (sIg) was first detected on fetal spleen cells at 45-50 days of gestation. SBU-T19 lymphocytes appeared later in gestation, being observed in fetal spleens at 57 days gestational age (g.a.). The distribution of T cells, B cells and MHC antigens in the developing spleen of the ovine fetus is described.

Animals↗

PubMed1987

Ontogeny of ovine lymphocytes. III. An immunohistological study on the development of T lymphocytes in sheep fetal lymph nodes.

The development of T lymphocytes in ovine fetal lymph nodes was studied immunohistologically using a panel of monoclonal antibodies. T lymphocyte subsets appeared within the ovine fetal lymph node in a specific sequence. SBU-T1- and SBU-T8-positive lymphocytes were seen at Day 47 of gestation. LCA, sIg, MHC I, MHC II, SBU-T6 and 46.66 antigens were also seen within the lymph node at this time. The first SBU-T4-positive cells were seen within the fetal lymph node at Day 50 of gestation, along with the first 20.96-, 25.69- and 38.38-positive cells. SBU-T19 lymphocytes appeared later in gestation, being present in fetal lymph nodes from Day 69 of gestation. The appearance and distribution of T and B cells in the developing lymph nodes of the ovine fetus is described and compared with the ontogeny of lymphocytes in the fetal thymus and spleen.

Animals↗

PubMed1987

Ontogeny of ovine lymphocytes. I. An immunohistological study on the development of T lymphocytes in the sheep embryo and fetal thymus.

The time of appearance of lymphocytes expressing T-cell markers and the subsequent development of the fetal thymus were studied in ovine embryos using a panel of monoclonal antibodies. Leucocyte common antigen (LCA) and major histocompatibility complex class I (MHCI) antigens were seen on a small number of cells within the ovine embryo at Day 19 of gestation. SBU-T6 (CD1)-positive cells were found at Day 22 of gestation, while major histocompatibility complex class II (MHC II) antigens were first observed at Day 25 of gestation. Large basophilic cells, weakly staining for SBU-T1 (CD5), were present in the mesenchyme of the neck and in the dorsal mediastinum and mesentery of embryonic sheep of 33 days gestational age (g.a.); however, no SBU-T1-positive cells were detected in the thymus at this time. No SBU-T4 (CD4)- or SBU-T8 (CD8)-positive cells were detected in any organs of embryos of this age. SBU-T4- and SBU-T8-positive cells were first seen in fetal thymi, and elsewhere within the fetus, at 35-38 days g.a. SBU-T19-positive cells were first seen within the fetal thymus at 50-58 days g.a.

Animals↗

PubMed1986

Thymocyte subpopulations during early fetal development in sheep.

Phenotypic analysis of thymocytes during fetal development may identify subpopulations which are either absent or difficult to detect in postnatal thymus. A panel of monoclonal antibodies specific for sheep lymphocyte antigens (SBU-T1, -T4, -T8, -T6) was used to identify thymocyte subpopulations in postnatal and fetal sheep. Thymuses were analyzed by two-color immunofluorescence and flow cytometry or by immunohistology. Two-color immunofluorescent staining of postnatal sheep thymus with anti-SBU-T4 and anti-SBU-T8 revealed four relatively distinct subpopulations with particular localizations: a) SBU-T4-T8-, predominantly outer cortex (12%); b) SBU-T4+T8+, inner cortex (74%); c) SBU-T4+T8-, medulla (10%), and d) SBU-T4-T8+, medulla (4%). One- and two-color immunofluorescent analysis of cells from early fetal thymuses demonstrated the appearance of SBU-T8+ cells well before SBU-T4+ cells. Immunohistologic staining of fetal sheep thymus at various stages of gestation (term = 150 days) revealed that lymphoid cells and MHC class II-positive dendritic cells first appeared at 35 days, at which stage the thymic epithelium was weakly positive for class I MHC antigens but negative for class II MHC antigens. The earliest lymphocyte antigens detectable on fetal sheep thymocytes were SBU-LCA and SBU-T1. By 40 days, the antigens SBU-T6, SBU-T4, and SBU-T8 were detectable on a small number of thymocytes; SBU-T8 preceded SBU-T4, and the number of SBU-T8+ thymocytes always exceeded the number of SBU-T4+ thymocytes throughout early gestation. At 50 days, a thymic medulla appeared and thereafter grew rapidly in size. Immunoperoxidase staining of serial sections of the fetal neck revealed cortical-type thymocytes outside the thymus from 40 days onward, before the appearance of a thymic medulla. However, by 60 days, only medullary-type thymocytes were observed either extrathymically or within the interlobular septa of the thymus, indicating that only thymocytes with a medullary phenotype leave the thymus from this stage of gestation.

Animals↗

PubMed1986

Three distinct subpopulations of sheep T lymphocytes.

Monoclonal antibodies reactive with distinct T lymphocyte subpopulations have been described in man, mouse and rat and structural analyses of these antigens have demonstrated a high degree of evolutionary conservation. This report describes the reactivity of three monoclonal antibodies (mAb), 19-19, alpha SBU-T4 and alpha SBU-T8, which define T cell subpopulations in the sheep. The mAb alpha SBU-T4 and alpha SBU-T8 define the sheep CD4 and CD8 molecules, respectively. These two antigens show similar tissue distributions, molecular weights and fluorescence-activated cell sorter profiles to human, mouse and rat CD4 and CD8 molecules. The mAb 19-19 is reactive with a subpopulation of T lymphocytes which displays a tissue distribution unlike that reported for a T cell subset in any other species. 19-19 stains 7% of efferent lymph lymphocytes, 15% of peripheral blood lymphocytes but only 1-3% of lymph node lymphocytes. Two-color immunofluorescence demonstrates that the 19-19+ T cell subset is SBU-T4- and SBU-T8-, and thus defines a third T cell subpopulation in sheep. Immunohistology on frozen lymph node tissue sections localizes 19-19 mAb-reactive cells to the subcapsular region of the lymph node and lymph node trabeculae. Only 1% of thymocytes are 19-19+ and these cells are located mainly in the medulla and often arranged as foci around blood vessels. The 19-19 mAb immunoprecipitates from sheep lymphocytes an antigen with an apparent molecular mass of 215 kDa under both reducing and nonreducing conditions. It is concluded that alpha SBU-T4 and alpha SBU-T8 recognize the sheep homologues of the human T4 and T8 antigens, respectively, whereas 19-19 recognizes an antigen (termed SBU-T19) which has not been reported in any other species.

Animals↗

PubMed1986

Four antigens expressed on most ovine cell types.

Monoclonal antibodies have been produced that bind to four different antigens expressed on the surface of ovine lymphocytes as well as to a variety of other ovine cell types. These antigens have been characterized with respect to their tissue distribution and immunochemistry. The timing of appearance of these antigens within the ovine embryo is reported.

Animals↗

PubMed1985

The sheep analogue of leucocyte common antigen (LCA).

The tissue distribution and immunochemical properties of antigens recognized by two monoclonal antibodies 1.11.32 and 1.28.124 define the sheep analogue of the leucocyte common antigen found in rat, man and mouse. Histological and immunofluorescent studies show that this antigen is found on all lymphocytes, as well as other leucocytes but is absent from non-leucocytic cells. Immunochemical data show that a series of proteins of high molecular weight (190,000-225,000) are recognized, and histological studies show the presence of this antigen on a subpopulation of fetal liver cells as early as Day 27-30 of gestation, and on all fetal thymocytes from Day 40 of gestation.

Animals↗

PubMed1985

Characterization of two sheep lymphocyte differentiation antigens, SBU-T1 and SBU-T6.

The monoclonal antibodies 25.91 and 20.27 define two lymphocyte cell surface antigens of sheep. 25.91 is reactive with 60-80% of lymphocytes and 98% of thymocytes, and only stains surface immunoglobulin-negative peripheral lymphocytes. 25.91 immuno-precipitates a 67,000 MW protein from lymphocyte lysates under both reducing and non-reducing conditions, whereas immunoprecipitation of thymocyte lysates reveals a 67,000, 62,000 MW complex. The tissue distribution and molecular weight analysis reported here for the antigen recognized by 25.91 indicate that this antigen is the sheep homologue of the human T1 and mouse Ly 1 antigens. The monoclonal antibody 20.27 is reactive with 80% of thymocytes and the majority of cell surface immunoglobulin-positive peripheral blood lymphocytes (B cells), but is unreactive with peripheral blood T cells. 20-27 also stains Langerhans cells in skin tissue sections and large dendritic-like cells in the paracortex sections and large dendritic-like cells in the paracortex of lymph node tissue sections. Immunoperoxidase staining of thymus tissue sections with 20.27 shows intense staining of cortical thymocytes and an absence of staining within the medulla. Molecular weight analysis of the 20.27 antigen reveals two major bands of 46,000 and 12,000 MW under both reducing and non-reducing conditions. The 20.27 antigen has properties resembling MHC class I-like antigens such as T6 in the human and TL in the mouse.

Animals↗

PubMed1985

Surface antigens, SBU-T4 and SBU-T8, of sheep T lymphocyte subsets defined by monoclonal antibodies.

Monoclonal antibodies have been used to characterize molecules found on the surfaces of T cells of sheep. SBU-T4 and STU-T8 are present on 80-85% of thymocytes, absent from B lymphocytes, and present on two-thirds and one-third of lymph node T lymphocytes, respectively. Double-labelling of T lymphocytes shows that the populations recognized are mutually exclusive. Immunoprecipitation of the SBU-T4 antigen from thymocytes and T lymphocytes reveals a molecule which migrates on SDS-PAGE as a single band of 56,000 MW under both reducing and non-reducing conditions. Under reducing conditions, the SBU-T8 molecule migrates as two bands of 33,000 and 36,000 MW when immunoprecipitated from thymocytes, but only the higher MW band is present following immunoprecipitation from peripheral lymphocytes. Under non-reducing conditions, SBU-T8 migrates as dimers and other multiples. Based on immunofluorescent, immunochemical and immunohistological data, these molecules are considered to be the structural analogues of the marker molecules used to delineate T-helper and T-cytotoxic/suppressor lymphocyte subsets of other species.

Animals↗

PubMedDate not supplied

Prospects for development of genetic markers for resistance to gastrointestinal parasite infection in sheep.

Selection of sheep for resistance to internal parasites represents a viable option for future parasite control. Many phenotypic measures are available for determining the level of infection in individual sheep, although no phenotypic markers are available which allow prediction of an individual's resistance status. Genetic markers are therefore the best way to incorporate parasite resistance into selection programmes. With the recent development of genetic maps, several experiments are underway to search for markers linked to parasite-resistance genes in sheep. It can be predicted confidently that markers associated with resistance will be discovered within 12 months. Markers useful as selection criteria will be available within 5 years, although considerable quantitative genetic analysis needs to be done to find the best way to utilise marker information in selection programmes. In future, methods for differential DNA analysis or mRNA expression will lead to isolation of the genes involved.

Animals↗