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Biomedical subjects

L Dudler

Publications and source records attributed to L Dudler.

46 records · Page 3Linked to original sources
PubMed1984

Differentiation of ovine immature B cells upon exposure to phorbol myristate acetate.

Immature B cells obtained from the ileal Peyer's patches ( IPPs ) of sheep, upon exposure to phorbol myristate acetate (PMA), expressed 20-30 times more sIgM per cell than nonstimulated IPP cells, and the sIgM level was the same as that of peripheral B cells. The exposure of IPP cells to PMA also induced IgM secretion. Macrophages were not required for the terminal differentiation of IPP cells in vitro.

Animals↗
PubMed1984

Differentiation of B lymphocytes in sheep. I. Phenotypic analysis of ileal Peyer's patch cells and the demonstration of a precursor population for sIg+ cells in the ileal Peyer's patches.

The ileal Peyer's patches (IPP) of sheep may be a primary lymphoid organ for b cells since they have a number of important features in common with the bursa of Fabricius of chickens. We have examined the surface phenotype of IPP cells. Approximately 90% to 95% of IPP cells are 'low sIgM+'; that is, they have surface IgM, but in much smaller amounts than peripheral B cells, which are 'high sIgM+'. IPP cells with sIgG or sIgA are very rare. Upon exposure to a tumour promotor, phorbol myristate acetate (PMA), in vitro, low sIgM+ cells differentiated into high sIgM+ cells. The amount of Ia-like antigens on the surface also increased after PMA treatment. Approximately 5% of IPP cells bore no identifiable markers. However, these cells could also be induced into high sIgM+ cells upon exposure to PMA; this may indicate the presence of precursors of sIgM+ cells within the IPP. While PNA (peanut agglutinin) binds strongly to the vast majority of IPP cells, it binds very little, if at all, to B cells obtained from the periphery, unless they have been treated with neuraminidase; this suggests that cells in the B lineage retain their PNA receptors, but that these become masked by sialic acid on mature B cells.

Animals↗
PubMed1984

Actin activity is high in the immunocompetent fraction of thymocytes.

We have shown previously that actin activity of lymphocytes correlates with their migratory abilities. To determine whether any subpopulation of thymocytes would possess the potential for peripheral migration, sheep thymocytes were separated into four fractions by Percoll discontinuous gradient centrifugation and actin activity of each fraction was determined. The fraction enriched for immunocompetent medullary-type cells showed the highest actin activity among thymocytes, but the activity was significantly lower than that of peripheral lymphocytes. The implications of the observation in relation to thymocyte migration is discussed.

Actins↗
PubMed1983

Studies on the differentiation of T lymphocytes in sheep. I. Recognition of a sheep T-lymphocyte differentiation antigen by a monoclonal antibody T-80.

The results presented in this paper demonstrate that a mouse IgM monoclonal antibody (T-80) recognizes an antigen on cells of the T-lymphocyte lineage of sheep. However, this antibody does not identify all T cells, as 10-20% of thymocytes and some peripheral-blood T cells are negative. T-80- thymocytes reside in the medulla. The majority of cortical thymocytes are T-80+ and classified as dull cells on the basis of antigen density per cell as measured by flow microfluorometry. In contrast, T-80+ cells in the periphery can be categorized into two populations, i.e., dull cells and bright cells. Suggestive evidence was obtained that bright T-80+ cells are fast recirculating T cells, whereas dull cells are sessile or less easily mobilizable T cells in the periphery. In foetal environment, over 90% of thymocytes and approximately 5% of spleen cells are T-80+ at 54 days of gestation (gestation period = 150 days), which may indicate that T-cell emigration from the thymus commences well before mid-gestation in sheep.

Animals↗
PubMed1982

T-cell recirculation in the sheep: migratory properties of cells from lymph nodes.

T lymphocytes derived from different sources in sheep were compared for their ability to recirculate from blood to lymph. Nylon wool columns were used to prepare T-cell-enriched populations from efferent intestinal lymph, efferent prescapular lymph and from cell suspensions of mesenteric lymph nodes and prescapular lymph nodes. With each animal, T cells from two of the above sources were labelled in vitro, one population with fluorescein isothiocyanate the other with rhodamine isothiocyanate; both populations were returned to the animal at the same time by intravenous injection. The intestinal lymph and prescapular lymph were continuously monitored to compare the recirculating properties of the two populations of T cells. This technique led to confirmation of the earlier reports in sheep of a preferential recovery of intestinal lymph T cells and of prescapular lymph T cells in the lymph from which the cells were originally collected. This phenomenon was much less evident with T cells from mesenteric nodes and prescapular nodes and in a number of experiments a random pattern of recirculation occurred. It is concluded that there are differences in the composition of the T-cell population in a node compared with that of the lymph draining the node. The advantages of using fluorescently-labelled cells to study lymphocyte migration are discussed.

Animals↗
PubMed1975

Humoral transmission of sleep. IX. Activity and concentration of the sleep peptide delta in cerebral and systemic blood fractions.

1. In order to obtain information about production and activity of the "sleep factor delta", characterized as oligopeptide with MW approximately 860, the peptide concentration (in nM/g dry dialysate) and the EEG delta activity of the corresponding dialysate (delta percent and integral of delta increase) were determined for cerebral blood from the dural venous sinus, systemic blood from the femoral vein and cerebrospinal fluid (CSF) from sleeping and alert rabbit donors. 2. Before hypnogenic or walking stimulation all hemodialysates exhibit a basic peptide concentration (26 nM/g dry dialysate) and a corresponding basic delta activity (231 muV X sec delta integral within 6 sec). 3. The electric thalamic stimulation of donors, with parameters inducing orthodox delta-sleep, parallely increases the delta peptide concentration (160 nM/g) and its activity (543 muV X sec delta integral) in cerebral blood dialysate. 4. The cerebral blood plasma dialyzed in vitro after hypnogenic thalamic stimulation exhibits a still higher peptide concentration (197 nM/g) and delta activity (804 muV X sec), increased at will by using a steeper diffusion gradient in the dialyzer (possibility of extracting more peptide). 5. By contrast, the systemic femoral blood plasma, similarly dialyzed in vitro develops a weaker delta activity (646 muV X sec) than cerebral blood plasma, in spite of a higher peptide concentration (275 nM/g). This dissociation suggests an activity marked by concomittant waking factors added to the cerebral blood during passage through the hindlimbs musculature. 6. The fact that cerebral blood dialyzed in vivo in walking donors has no delta activity (-313 muV X sec) in spite of a minimal delta peptide concentration (10 nM/g) confirms the assumption that walking factors may mask the peptide activity. Additionally, it shows that they may also antagonize the peptide production. The sleep cycle seems to be regulated not only by neural, rapid acting antagonistic mechanisms, but also by humoral, slower acting antagonistic factors. 7. Cerebrospinal fluid withdrawn from sleeping donors induces insignificant changes in recipients, probably because of too small a peptide concentration in this fluid.

Animals↗
PubMedDate not supplied

An enhanced role for the recirculating lymphocyte in the neonatal immune system.

Lymphocytes continually recirculate between the blood and the tissues via the lymph independent of antigen. A great deal is known regarding both the physiology and the molecular mechanisms responsible for the process in adults. However, relatively little is known regarding the development of the recirculating lymphocyte pool in very young animals or fetuses. We have directly measured the recirculation of lymphocyte subsets in antigen-inexperienced newborn animals, and found extensive recirculation of T cells through both intestinal and subcutaneous lymph nodes. Apparent selective migration of recirculating lymphocytes could be attributed to subset-specific migration of gammadelta-T cells through subcutaneous lymph nodes. This clearly demonstrates that the preference for gammadelta-T cells to recirculate through SCLN is lineage specific, and independent of the presence of antigen. Most surprising was the observation that the recirculating lymphocyte pool was proportionately larger in neonatal animals than in adults, which correlated with the histological appearance of newborn lymph nodes. This data strongly suggests that development of the recirculating lymphocyte pool is inversely correlated with antigen exposure, and decreases in size with age and the acquisition of immunological memory.

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