Phenotypic analysis of the chicken thymic microenvironment during ontogenic development

The development of monoclonal antibodies (mAb) reactive with the thymic microenvironment has identified distinct subpopulations within the stromal component, but the function of these subregions in intrathymic T-cell differentiation remains essentially an enigma. In this study, we have used such a panel of mAb to examine the chicken thymus during ontogenic development to gain insight into the contributions of these thymic regions to the distinct phases of T-cell development and to further characterize the development of this organ. Our reagents have demonstrated the complex differentiation of the primitive endodermal epithelium into more specialized structures and the development of other thymic stromal components from mesectodermal cells. We also describe molecules localized to the subcapsular and perivascular regions, which have an ontogenic expression corresponding to the early localization and stimulation of thymic precursors and another molecule on the medullary vasculature expressed corresponding to the exit of mature cells from the thymus. In addition, two markers of distinct medullary epithelial clusters are initially expressed corresponding to the appearance of T-cell receptor-1 (TcR-1) and TcR-2 positive cells in the medulla, respectively. These mAb potentially represent excellent reagents for further definition of the thymic modulation of T-cell differentiation.

Phenotypic characterization of chicken thymic stromal elements

Phenotypic profiles of the thymic stromal components provide an excellent approach to elucidating the nature of the microenvironment of this organ. To address this issue in chickens, we have produced an extensive panel of 18 mAb to the thymic stroma. These mAb have been extensively characterized with respect to their phenotypic specificities and reveal that the stromal cells are equally as complex as the T cells whose maturation they direct. They further demonstrate that, in comparison to the mammalian thymus, there is a remarkable degree of conservation in thymic architecture between phylogenetically diverse species. Eleven mAb reacted with thymic epithelial cells: MUI-73 was panepithelium, MUI-54 stained all cortical and medullary epithelium but only a minority of the subcapsule, MUI-52 was specific for isolated stellate cortical epithelial cells, MUI-62, -69, and -71 were specific for the medulla (including Hassall's corpuscle-like structures), MUI-51, -53, -70, and -75 reacted only with the type-1 epithelium, or discrete regions therein, lining the subcapsular and perivascular regions and MUI-58 demonstrated the antigenic similarity between the subcapsule and the medulla. Seven other mAb identified distinct isolated stromal cells throughout the cortex and medulla. Large thymocyte-rich regions, which often spanned from the outer cortex to medulla, lacked epithelial cells. These mAb should prove invaluable for determining the functional significance of thymic stromal-cell subsets to thymopoiesis.

Use of the Mycosep multifunctional cleanup column for liquid chromatographic determination of aflatoxins in agricultural products

A liquid chromatographic (LC) technique has been developed that uses the Mycosep multifunctional cleanup (MFC) column. MFC columns provide a rapid 1-step extract purification. They are designed to retain particular groups of compounds that may create interferences in analytical methods. At the same time, MFC columns allow compounds of interest to pass through. In the method presented, test samples are extracted in a blender with acetonitrile-water (9 + 1). A portion of the extract is forced through an MFC column designed especially for analysis of numerous mycotoxins. Analytical interferences are retained, while aflatoxins pass through the column. Aflatoxins B1 and G1 are converted to their hemiacetals by heating a mixture of purified extract and water-trifluoroacetic acid-acetic acid (7 + 2 + 1) at 65 degrees C for 8.5 min. An aliquot of this mixture is analyzed by isocratic LC with acetonitrile-water mobile phase and fluorescence detection. A detection limit of less than 0.5 ng/g for aflatoxin B1 was obtained. Average recoveries greater than 95% total aflatoxins (B1, B2, G1, and G2) and coefficients of variation of less than 3% were obtained. The method was successfully applied to the following commodities: corn, almonds, pista-chios, walnuts, peanuts, Brazil nuts, milo, rice, cottonseed, corn meal, corn gluten meal, fig paste, and mixed feeds.

Abnormalities associated with the bursal microenvironment in spontaneous dysgammaglobulinemia of UCD line 140 chickens

UCD line 140 chickens have been previously reported to develop a syndrome of spontaneous 7s immunoglobulin deficiency and the presence of autoantibodies. Earlier studies demonstrated that these inbred birds have normal peripheral blood T and B cell numbers; they also respond normally to allogeneic stimulation. Although the 7s immunodeficiency does not manifest itself until several months of age, line 140 birds have a premature degeneration of bursa. Because of the recent development of monoclonal reagents specific for bursal elements, including surface epithelium, basement membrane associated epithelium, follicle associated epithelium, and lymphoid subpopulations, we have examined line 140 and control birds for the expression of bursal epithelial cell antigens. Line 140 birds, in contrast to control chickens, have a dramatic early alteration in the expression of an epithelial cell marker in the bursa, thymus, and intestine. Moreover, to further address this issue, we transplanted bursa from 10-day embryos onto the chorioallantoic membrane, a privileged site. Bursae from control birds became abnormal when transplanted onto line 140 CAM; they remained normal when transplanted among several control chicken lines. In contrast, line 140 bursa remained abnormal independent of the transplant procedure. Due to the marked bursal abnormality observed specific to the dysgammaglobulinemia chicken line, we propose that the microenvironmental features of line 140 bursa may predispose these birds to the development of humoral immunodeficiency and autoantibodies.

Selective abnormalities in the thymic microenvironment associated with avian scleroderma, an inherited fibrotic disease of L200 chickens

As a prelude to deciphering the mechanisms of intrathymic T-cell maturation we produced a panel of 18 monoclonal antibodies (mAbs) against chicken thymic stromal elements. Eleven of these detected epithelial cells. They were: pan-epithelial; subcapsule and peri-vascular (pan type 1 epithelium); subcapsular, perivascular and medulla; medulla; or cortex. Of particular interest were the sub-specificities within these regions, especially the subcapsular region. Four mAbs stained both epithelial and non-epithelial cells in discrete regions. In addition, three mAbs recognized only non-epithelial cells. One identified macrophages scattered throughout the thymus, another the connective tissue and another the medullary vascular endothelium. These reagents have provided an extensive profile of the thymic stromal architecture and revealed that these cells are equally as complex as the T cells whose differentiation they induce and regulate. While the mAbs provide a valuable means for studying the mechanisms of normal thymopoiesis, their clinical significance is unknown. UCD line 200 chickens develop an autoimmune disease manifest by dermal and internal organ fibrosis, T cell infiltrates of skin and other affected organs and production of multiple autoantibodies. We have used our panel of mAbs to evaluate the thymic microenvironment in these autoimmunity-prone chickens. A comparative analysis with control chickens revealed striking deficiencies in the L200 subcapsular regions coupled with excessive expression of MHC class II antigens, particularly in the cortex. We hypothesize that these abnormalities induce altered T-cell differentiation, thereby predisposing the L200 chickens to autoimmune disease.

Ontogeny of T cell development in avian scleroderma

UCD line 200 chickens develop an inherited fibrotic disease associated with the production of antinuclear antibodies, antibodies to type II collagen, and early skin lesions characterized by intense T lymphocyte infiltrates. In the present study we have investigated the hypothesis that developmental abnormalities in T lymphocyte differentiation predispose the line 200 chickens to autoimmune disease. The status of the thymic microenvironment in these birds during ontogeny was studied with an extensive panel of monoclonal antibodies (mAbs) reactive with distinct stromal cell subsets including MHC determinants. In addition, their T-cell graft-versus-host reactivity and responses to mitogenic stimulation and interleukin (IL)-2 were also analyzed. Line 200 chickens have profound defects in thymic structure with a virtual complete absence of antigens specific for type I epithelium which lines the thymic subcapsular and perivascular regions. There are excessive levels of MHC class II positive cells, particularly in the cortex, and B cells/subset macrophages identified by mAb MUI 36. These defects are found from the late embryonic period, long before clinical disease is manifest. Furthermore, by FACS analysis, line 200 thymocytes have a major increase in IL-2 receptor density. In addition, line 200 chicken peripheral blood lymphocytes (PBL) respond poorly to mitogenic agents and have a reduced response to IL-2. Finally, it is important to note that line 200 PBL produce a normal graft-versus-host reaction. We propose that these abnormalities in T-cell differentiation are selective, not global, and may be reflective of a defect in thymic education resulting in an inappropriate response to self-antigens.

Cyclophosphamide- and testosterone-induced alteration in chicken bursal stroma identified by monoclonal antibodies

Both cyclophosphamide (Cy) and testosterone propionate (TP) treatments ablate B cells in chickens. Essential bursal microenvironmental elements, however, are altered or lost following TP treatment, while bursae from Cy-injected birds can be reconstituted with donor precursors. These two models can thus be utilized to distinguish which bursal stromal molecules are functionally most important in the specific microenvironment of this organ. Monoclonal antibodies (mAb) reactive with non-lymphoid components of the chicken bursa of Fabricius have been used to examine bursal sections from birds treated with Cy or TP. Molecules have been identified on the epithelial buds and follicle-associated epithelium (FAE) that are enhanced following Cy treatment (MUI-52 and 58) and are absent in TP-treated birds. The expression of these molecules may correspond to the ability of Cy-treated but not TP-treated bursae to attract lymphoid precursors. Molecules have also been identified on cells in the subepithelial mesenchymal layer (MUI-63, 65 and 75). These cells interact with the surface epithelium (sEp) prior to epithelial bud formation, an interaction which appears to be TP sensitive. Additionally, two potentially important molecules have been identified in the bursal medulla (MUI-54 and 72) which may have an interactive role with developing B lymphocytes.

The phenotypic heterogeneity of mouse thymic stromal cells

Sixteen monoclonal antibodies (mAb) were produced against mouse thymic stromal elements. These mAb fell into two groups of reactivity: (i) thymic epithelial markers (screened and presented according to the guidelines proposed in the 1989 Rolduc Thymic Epithelial Workshop); and (ii) non-epithelial thymic markers. Specificities of these mAb included extensive subpopulations of both epithelial and non-epithelial thymic stromal cells, as well as isolated stromal cells, demonstrating some of the complex microspecificities in existence within the thymic microenvironment. Furthermore, six of these mAb demonstrated shared antigenicity between thymocytes and thymic stromal cells, revealing greater similarities than previously recognized between these two components. Three mAb detected antigens illustrating three consecutive layers of the blood-thymus barrier: the vascular endothelium; connective tissue of the capsule and perivascular spaces; and the connective tissue associated with the basal laminae lining these regions. This study illustrates unequivocably that there are indeed complex and varied microenvironments existing within the thymus, and emphasizes the need for reclassification of these cells.

The ontogeny of chicken bursal stromal cells defined by monoclonal antibodies

Molecules expressed on lymphoid stromal cells influence the differentiation of lymphocytes. We have examined the expression of stromal markers, identified by monoclonal antibodies, in the chicken bursa of Fabricius during ontogenic development. These results are also consistent with the hypothesis that medullary secretory cells are of mesenchymal origin, whereas the basement membrane-associated and some medullary epithelium are derived from the endoderm. Our results have demonstrated the complexity of bursal stromal development with determinants expressed on the adult medullary stellate cells (e.g., MUI-57 and 62) and cortical macrophages (e.g., MUI-66 and 72) detected on the early embryonic tunica propria (e.g., MUI-57, 66 and 72) or surface epithelium (e.g., MUI-62 and 66). In addition, we provide preliminary evidence regarding potential functions of these molecules in stem cell colonization (MUI-52), early B-cell differentiation (e.g., MUI-72), late bursal B-cell development (MUI-69 and 71) and the follicle-associated epithelium transport mechanism (MUI-61 and 73).

Phenotypic characterization of chicken bursal stromal elements

Many, if not all, of the different phases of intrabursal B-cell maturation are controlled by the stromal components. We have used an extensive panel of mAb to provide a detailed phenotypic profile of these cells. Antigenic specificities were defined for the entire surface epithelium, interfollicular surface epithelium, follicle-associated epithelium, basement membrane, basement membrane-associated epithelium. Several mAb were specific for the medulla, including those reactive with the stellate network of epithelial cells, isolated macrophages, and granular, apparently secreted antigens. One of these, MUI-92, appears to be bursa-specific. Two mAb reacted strongly with stellate cortical macrophages, one of which weakly stained similar cells in the medulla. MHC-class II antigens were expressed on endothelium of the corticomedullary junction, macrophagelike cells in the cortex, and medulla and B lymphocytes predominantly in the cortex. Collectively, these mAb have demonstrated the antigenically distinct nature of discrete regions in the bursa, but also the continuity of the surface epithelium with the corticomedullary junction and medulla. They represent excellent reagents for defining the stromal cell contribution of B-cell development.

Surgical treatment of chronic pancreatic cholangiopathy

In a consecutive surgical series of 70 patients with chronic calcifying pancreatitis, 18 presented with fixed stenosis of the terminal common bile duct. Nine patients presented with jaundice and two had a palpable gallbladder. The most relevant laboratory datum in the series was a persistently high serum alkaline phosphatase level. Long tapering of the terminal common bile duct was the characteristic radiological sign in 45 of our patients. In five of the 18 cases compression of the terminal bile duct was due to cephalic pseudocysts. Hepaticojejunostomy-en-Y was the type of drainage chosen in 16 cases, and an end-to-side technique was used in 15 patients. Side-to-side choledochoduodenostomy was performed in two cases. In 14 patients, biliary drainage was associated with other surgical procedures on the pancreatic parenchyma. No postoperative complications due to the biliary drainage occurred in this series.

The sequence of the mouse 14 kDa beta-galactoside-binding lectin and evidence for its synthesis on free cytoplasmic ribosomes

The partial amino acid sequence of the mouse 14 kDa beta-galactoside-binding lectin has been deduced from cDNA clones corresponding to 86% of the coding sequence and extending to the polyadenylation signal. The deduced amino acid sequence for the murine lectin shows 94% identity with the rat, 89% with human, 86% with bovine and 46% with the chicken 14 kDa lectins. A cDNA probe has been used to analyse genomic DNA and identify a single mRNA of approx. 570 bp in 3T3 fibroblasts, murine erythroleukaemia cells and the murine basement-membrane-secreting Engelbreth-Holm-Swarm tumour. Analysis of free and bound polyribosomes has shown that the lectin message is translated on free cytoplasmic ribosomes.

Effects of urogastrone (epidermal growth factor) on the intestinal epithelium

Recombinant urogastrone (human epidermal growth factor) was infused into rats in which intestinal cell proliferation was reduced to a steady state basal level by feeding them intravenously. Urogastrone elevated the augmented metaphase index and weight of all sections of the gastrointestinal tract in a dose-related manner. Infusion of urogastrone at a dose which has a minimal effect on gastric acid secretion significantly increased crypt cell production and tissue weights throughout the gastrointestinal tract. Intravenous urogastrone was also effective in restoring cell proliferation after the intestine had become hypoproliferative. Urogastrone administered luminally had no significant effect on either intestinal weight, crypt cell production rate, or metaphase collection.

Epidermal growth factor selectively increases maltase and sucrase activities in neonatal piglet intestine

1. Pig intestinal sucrase and maltase activities increase markedly, and lactase activity decreases, during the second week of post-natal life. Correlations noted between the time course describing these changes and that found previously to describe a decline in the ability of the pig intestine to take up macromolecules suggest that both events are subject to the same type of developmental control. 2. Injection of epidermal growth factor (EGF) into 3-day-old piglets increase sucrase and maltase activities measured 3 days later. These increases, which are not seen when measuring other hydrolase enzymes, are confined to the mid and distal regions of the small intestine. 3. Dexamethasone injected into 3-day-old piglets inhibits lactase and, on occasion, sucrase activities without affecting other intestinal hydrolases. Significant increases in sucrase and maltase activities also occur in distal intestine following injection of EGF plus dexamethasone into 3-day-old pigs. 4. Cytochemical analysis shows EGF effects on sucrase and maltase activities to be exerted in crypt and basal villus enterocytes produced post-natally. Dexamethasone inhibits lactase activity mainly by acting on mid and upper villus enterocytes produced before birth. 5. EGF appears to increase sucrase and maltase activities by extending the time during which young enterocytes continue to accumulate these enzymes in their brush-border membranes. Dexamethasone appears to cause a more fundamental change in the biochemistry of older enterocytes. accompanied by an increasing ability of these cells to transport neutral amino acids through a sodium-dependent mechanism (see James, Smith, Tivey & Wilson, 1987a).

Dexamethasone selectively increases sodium-dependent alanine transport across neonatal piglet intestine

1. Lysine and alanine uptake by pig enterocytes has been measured in piglet mid intestine both during normal development and 3 days after injection of dexamethasone and epidermal growth factor (EGF) into 3-day-old animals. 2. Alanine uptake measured in the presence of sodium increased markedly during the first 4 weeks of post-natal life. Similar effects on alanine uptake could be produced through injection of dexamethasone, but not EGF, into 3-day-old piglets. Alanine uptake measured in the absence of sodium and lysine uptake measured in the presence of sodium remained unchanged during development and unaffected by injection of dexamethasone or EGF. 3. Enterocytes capable of transporting alanine in the presence of sodium were found, by quantitative autoradiography, to cover the top 400 micron of the villus in 6-day-old and 3-4-week-old control pigs. Alanine concentrations in villus tip enterocytes in 3-4-week-old pigs were four times those found in 6-day-old animals. Qualitative examination of selected villi, however, showed alanine uptake taking place over a considerably greater area of villus surface in 6-day-old compared with 3-4-week-old animals. 4. Injection of dexamethasone and EGF into 3-day-old piglets caused an increase in crypt depth without apparent change in crypt cell proliferation. The rate at which enterocytes migrated out of the crypt and the length of individual villi also remained unchanged by dexamethasone or EGF injection. 5. Dexamethasone produces its effect on alanine uptake by acting on older enterocytes present on the upper part of the villus. These enterocytes can be shown, by calculations based on enterocyte migration rate, to have already been present on the villus at the time the pig was born. 6. The above findings are discussed in relation to the ability of villus as well as crypt enterocytes to change their programme of differentiation in response to external stimuli. The particular ability of dexamethasone to induce system A type carrier function is further discussed in relation to normal changes found to occur during neonatal development. It is finally suggested, as a working hypothesis, that endogenous glucagon might act as the final mediator of both developmentally controlled and dexamethasone-induced changes in amino acid transport.

Intravenous but not intragastric urogastrone-EGF is trophic to the intestine of parenterally fed rats

The effects of beta-urogastrone/human epidermal growth factor (URO-EGF) on intestinal epithelial cell proliferation were studied in rats in which intestinal cell proliferation had been reduced to a steady state basal level, by maintaining the rats on total parenteral nutrition. The accumulation of arrested metaphases over a two hour time period was determined in a dose response study. Increasing doses of URO-EGF progressively raised the two hour collection of metaphases and intestinal weights. Intravenous infusion of URO-EGF was also effective in restoring cell proliferation when it was infused after the intestine had become hypoproliferative. beta-urogastrone/human epidermal growth factor administered through an intragastric cannulae thrice daily had no significant effect on intestinal weight or crypt cell production rate or metaphase collection. It is proposed that one of the in vivo actions of urogastrone-epidermal growth factor is the maintenance of gastrointestinal growth and that this occurs through a systemic rather than a luminal mechanism.

Proliferative effects of urogastrone-EGF on the intestinal epithelium

The effects of B-urogastrone/human epidermal growth factor on intestinal epithelial cell proliferation were studied in rats in which intestinal cell proliferation was reduced to a steady state basal level (by maintaining the rats on total parenteral nutrition). Increasing doses of urogastrone progressively raised the two hour collection of metaphases and intestinal weights. The crypt cell production rate was measured in animals maintained parenterally with or without urogastrone, and in rats fed a standard laboratory ration. Continuous infusion of 15 micrograms per rat per day of recombinant beta urogastrone (a dose which has a minimal effect on gastric acid secretion) significantly increased cell proliferation and intestinal tissue weights throughout the gastrointestinal tract. Intravenous infusion of urogastrone was also effective in restoring cell proliferation when it was infused after the intestine had become hypoproliferative. Urogastrone administered through an intragastric cannula thrice daily had no significant effect on either intestinal weight, crypt cell production rate, or metaphase collection.

Stimulation of direct embryogenesis from mesophyll protoplasts of Medicago sativa

Mesophyll protoplasts of Medicago sativa were exposed to low voltage electrical fields immediately following isolation. Several exposure times and voltages were utilized. At the lower doses, protoplast aggregation and subsequent embryogenesis were stimulated. A clone of 'Rangelander', which was directly-embryogenic (i.e. embryos were derived from single mesophyll protoplasts without an intervening callus phase), was induced to form embryos in all samples exposed to the lowest level electrical fields, while unexposed controls formed few or no embryos. A clone of 'Regen S', which was previously not directly-embryogenic, was induced to follow the 'Rangelander' pattern of development and to produce early globular embryos.

Urogastrone-epidermal growth factor is trophic to the intestinal epithelium of parenterally fed rats

The weight of the stomach, small intestine and colon and the mucosal crypt cell production rate of these tissues were significantly decreased after 10 days on an isocaloric TPN diet when compared to orally fed controls. Continuous infusion of recombinant beta urogastrone, at a dose below that needed to inhibit gastric acid secretion, largely prevented this decrease in crypt cell production rate and gastrointestinal tissue weights.

Use of a mouse chimaeric model to study cell migration patterns in the small intestinal epithelium

The pattern of cells migration in the small intestinal epithelia of a RIII/ro----C57BL/6J mouse aggregation chimaera is demonstrated using Dolichos biflorus agglutinin-peroxidase (DBA) conjugate as a strain-specific marker. Using serial tangential sections of heterogeneously stained villi and plotting the distribution of labelled/unlabelled cells with a drawing tube, and by three-dimensional reconstruction with the aid of computer graphics, we show the migration pathway to be in tight cohorts of similar DBA-peroxidase staining type, which move upwards in straight lines. There is little cell mixing either on the villus or along the crypt-villus junctions. Our observations also show for the first time that a single crypt can feed cells to more than one villus. They also suggest that either cell loss is not confined to the villus tips but can take place from the villus sides, or that there is marked asynchrony of cell production between crypts.

Relationship between platelet count and cardiotomy suction return

A simple, inexpensive, accurate method of measuring the amount of blood returned by the cardiotomy suction system was devised and calibrated. Preoperative and postoperative platelet counts were obtained in 76 patients with congenital heart disease in whom the amount of cardiotomy suction return was measured. The mean percentage of total perfusate returned by the cardiotomy suction system was 8.9%. Both postoperative platelet count and the percentage change between preoperative and postoperative platelet counts correlated with the amount of blood returned by the cardiotomy suction system, time on bypass, and the percentage of total perfusate aspirated by the system.