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Biomedical subjects

R W Leid

Publications and source records attributed to R W Leid.

At least 55 records · Page 3Linked to original sources
PubMed1985

Inhibition of rat peritoneal mast cell histamine secretion by protoporphyrin and incandescent light.

Rat peritoneal mast cells (RPMC) exposed to protoporphyrin (PP) and incandescent light (IL) become refractory to the stimulatory effects of compound 48/80. Once initiated, this refractory state continues to develop even after removal of the light source and is essentially complete within 30 min. While this state of unresponsiveness appears to be relatively permanent in the dark, prolonged incubation in the light (greater than 80 min) induces cell lysis. We have shown that the resistant state is not specific for the mast cell stimulator compound 48/80. Mast cells passively sensitized with IgE and illuminated for 30 min in the presence of 100 ng/ml PP also fail to release histamine upon stimulation by anti-rat IgE, anti-rat F(ab')2, concanavalin-A (Con-A), and the calcium ionophore A23187. The inability to respond to immunological stimuli could not be ascribed to the reversible loss of membrane-bound IgE from its receptor. While the binding of either the inducer to IgE or IgE to its receptor may actually be impaired in refractory cells, the significance of such impairments on the development of the resistant state in these cells is precluded by the inability of A23187 to either increase intracellular 45Ca2+ levels or induce histamine release. The data suggest that the RPMC refractory state develops as a result of covalent inter- and/or intramolecular cross-linking of membrane proteins. Furthermore, this cross-linking may involve sulfhydryl or amino groups essential to either stimulus transduction, or the histamine secretory process itself.

Animals↗
PubMed1985

Onchocerca cervicalis in horses: dermal histopathology.

A histopathological study of ventral midline skin from midwestern U.S. horses with and without onchocerciasis due to Onchocerca cervicalis found perivascular mononuclear dermatitis as the most consistent difference between the two groups. Seasonal variation in parasite numbers or cellular influxes was not observed. Eosinophilic dermatitis was observed in horses with onchocerciasis and dermatitides of unknown etiology.

Animals↗
PubMed1985

Stimulation of equine eosinophil migration by hydroxyacid metabolites of arachidonic acid.

Lipoxygenase products of arachidonic acid are important mediators of inflammation, affecting several aspects of cell function. Monohydroxyeicosatetraenoic acid (mono-HETE) and 5,12-dihydroxyeicosatetraenoic acid (LTB4) enhance migration of both neutrophils and eosinophils in several species. The relative ability of positional isomers of HETE and of LTB4 to affect migration of equine eosinophils was studied. The 5, 8, 9, 11, 12, and 15 isomers of HETE were prepared by autooxidation of arachidonic acid, separated by sequential normal phase and reverse phase high performance liquid chromatography, and their identities verified by gas chromatography-mass spectrometry. Equine eosinophils were isolated to 30-70% purity on discontinuous metrizamide gradients. All isomers of HETE stimulated directed migration (chemotaxis) at concentrations ranging from 10(-5) to 10(-8) M. The relative activities of isomers were 11 greater than 9 = 8 = 5 greater than 12 greater than 15. The dihydroxy acid LTB4 maximally stimulated chemotaxis of equine eosinophils at a concentration of 3 X 10(-7) M. The eosinophil migration that resulted was less than the maximal stimulation observed in response to isomers of HETE. The results of our study suggest that equine eosinophils are excellent indicator cells for assay of arachidonic acid metabolites with chemotactic activity. Equine eosinophils are more sensitive to chemotactic stimulation by HETEs than cells from other animal species but are far less sensitive to stimulation by LTB4.

Animals↗
PubMed1984

Isolation and partial characterization of bovine and equine factor D.

Bovine and equine factor D were purified to apparent homogeneity as evidenced by a single protein staining band on 7.5-17.5% SDS-PAGE slab gels under both reducing and non-reducing conditions. An apparent mol. wt of 15,000 for bovine D and 22,500 for equine D were noted after SDS-PAGE gel analysis of both reduced and non-reduced preparations. A single polypeptide chain for both proteins was evidenced by the lack of any change in the electrophoretic mobility under each of these conditions. The bovine and equine D were enriched 3347- and 9447-fold, with a 20 and 29% yield of hemolytic activity, respectively. Functionally, both equine and bovine D would reconstitute a human reagent deficient in D (RD), while human or equine D would substitute for bovine D when using a bovine RD. Neither bovine, equine or human D would, however, reconstitute an equine RD.

Animals↗
PubMed1984

Immunoglobulin levels in tears and aqueous humor of horses before and after diethylcarbamazine (DEC) therapy.

A quantitative investigation of equine tear and aqueous humor immunoglobulins was done using normal horses and ponies as well as horses and ponies infected with Onchocerca cervicalis. The equine immunoglobulin isotypes IgGa, IgM, IgA and IgG(T) were quantitated by either single radial immunodiffusion (SRID) or radioimmunoassay (RIA). Tear immunoglobulin levels for IgGa (128 +/- 151 micrograms/ml), IgA (1,664 +/- 1,038 micrograms/ml) and IgM (106 +/- 74 micrograms/ml) were measured, while IgG(T) was not detectable. In horses with ocular inflammation the IgGa was 18-fold higher in the tears, 2,269 +/- 3,077 micrograms/ml. Aqueous humor obtained by paracentesis of the normal equine eye under anaesthesia, resulted in values for IgGa (45.2 +/- 20.0 micrograms/ml), IgG(T) (5.2 +/- 2.0 micrograms/ml), IgM (1.3 +/- 4.8 micrograms/ml) and IgA (0.8 +/- 1.0 micrograms/ml). A pooled sample of normal aqueous fluid obtained from over 100 horses at an equine abbatoir in Indiana gave values of 1,150 micrograms/ml for IgGa, 65 micrograms/ml for IgG(T), 2.5 micrograms/ml for IgA and 3.0 micrograms/ml for IgM. In animals infected with 0. cervicalis and treated with Diethylcarbamazine (DEC), there was a marked elevation of IgGa and IgG(T) in the tears and aqueous humor while IgA and IgG(T) were also elevated slightly in the aqueous. The findings of elevated immunoglobulin isotypes in the aqueous humor may not be related to the DEC treatment and 0. cervicalis infections but rather to repeated paracentesis and the development of acute inflammation of the equine eye as a result of the trauma of paracentesis. The elevations in equine immunoglobulin isotypes in the tears after DEC treatment are not subject to the same caveat. The preferential elevation in IgGa and IgG(T) in the tears precedes the development of corneal opacities observed in the same horses. The concentration of specific antimicrofilarial antibody in these tears remains to be determined but may well account for a major share of the total immunoglobulins detected.

Animals↗
PubMed1984

Aggregation of bovine platelets by acetyl glyceryl ether phosphorylcholine (platelet activating factor).

Platelet activating factor is a multifaceted mediator of inflammation capable of stimulating platelet aggregation as well as anaphylaxis, neutropenia and numerous other in vitro and in vivo cellular changes. This lipid mediator, or autocoid, is released by a wide variety of inflammatory cells following an equally diverse group of cellular stimuli including phagocytosis or antigenic stimulation. The synthesized form of PAF is acetyl glyceryl ether phosphorylcholine (AGEPC). In this study AGEPC aggregated bovine platelets in a dose dependent manner. Maximal, irreversible aggregation occurred at 3.6 X 10(-11) M AGEPC with unwashed platelets and at 8.8 X 10(-12) M AGEPC with washed platelets. Aggregation failed to occur when platelets were tested with the biologically inactive structural analog of AGEPC. The possible contribution by platelet cyclooxygenase products was eliminated by showing lack of platelet aggregation to arachidonic acid and also by pretreating platelets with aspirin.

Animals↗
PubMed1984

A review of the antigens of Fasciola hepatica.

The interaction between the antigens of Fasciola hepatica and the host immune response are reviewed. This paper evaluates not only more recent work, but the older literature as well. Antigens from each stage in the life cycle are considered with the idea of identifying those antigens with a potential for use in an effective vaccine. Antigens which cross-react with other parasite species are detailed as well as those that cross-react between different stages in the life cycle of F. hepatica. The objective of the review is to demonstrate for other investigators that vaccination against F. hepatica is a distinct possibility. We hope to encourage more investigators to initiate work on this aspect of an economically-important cosmopolitan parasite.

Animals↗
PubMed1984

Effect of inoculum on the size and location of Fasciola hepatica subsequently recovered from the livers of rats.

Two outbred strains of Sprague-Dawley rats were given, by intraperitoneal injection, 5, 10, 20, 30 or 50 newly excysted juvenile (NEJ) Fasciola hepatica. Ninety days post-infection all rats were killed and their livers teased apart under 10 X magnification for quantitation of the flukes present. There was no significant difference in worm numbers between the rat strains. However, several significant differences (P less than 0.05) between the various infection groups were observed. As the size of the infective dose was increased from 5 to 50 NEJ, the percentage of the infective dose recovered from the livers of the infected rats decreased from 36.7 to 12.1%. With the 5 and 10 NEJ infective doses, the worms recovered were large mature flukes (1.52 and 1.68 cm, respectively) and were found in the common bile ducts. In the rats receiving infections of 30 and 50 NEJ, the flukes were smaller (0.88 and 0.55 cm, respectively), immature, and were primarily located in the liver parenchyma. These findings are important in light of previous studies on the development of resistance in the rat to challenge infections in which immunity was based on both the size and the location of the flukes recovered. The results from our study indicate that in a primary infection of 20 or greater NEJ, many small immature flukes remain in the liver parenchyma, even after several months. When testing for resistance to F. hepatica in rats, these flukes may erroneously be thought to comprise a portion of the challenge infection.

Animals↗
PubMed1984

Bovine pulmonary alveolar macrophages: antemortem recovery and in vitro evaluation of bacterial phagocytosis and killing.

A system was developed to recover pulmonary alveolar macrophages (PAM) from living cattle and to evaluate the function of these cells by measuring bacterial phagocytosis and killing. For the collection of PAM, single-tube and telescoped double-tube pulmonary lavage devices were compared. The total recovery, using these systems, was 70 +/- 10.7% of infused fluid, yielding approximately 87% PAM. The total number of cells per collection was approximately 5 times higher with the single-tube device (6.87 +/- 0.78 x 10(7) cell/ml) than with the telescoped double-tube device (1.3 +/- 0.1 X 10(7) cells/ml). Phagocytosis and intracellular killing of Staphylococcus epidermidis and Staphylococcus aureus by PAM in media suspension and by plastic-adherent PAM were evaluated. In addition, different bacteria-to-macrophage ratios were assessed, as well as the intracellular killing of S epidermidis at periodic intervals. Results showed that over a 3-hour period, similar numbers of both bacteria were phagocytized, but intracellular killing of S epidermidis was more efficient than intracellular killing of S aureus. It also was found (i) that suspended PAM and adherent PAM phagocytized similar numbers of bacteria; (ii) that when the bacteria-to-cell ratio was 10:1, the numbers of phagocytized bacteria and intracellular killing were higher than when the ratio was 1:10; and (iii) that killing of S epidermidis by adherent PAM was directly proportional to incubation time. The time that PAM are in culture affects the phagocytosis and killing of intracellular bacteria, as shown by increased phagocytosis and by intracellular killing of S epidermidis by PAM in suspension for 48 hours or plastic adherent for 60 hours after collection.

Animals↗
PubMed1984

Inhibition of antigen- and lectin-induced proliferation of rat spleen cells by a Taenia taeniaeformis proteinase inhibitor.

Rat splenic lymphocytes, cultured in vitro for 3 days in the presence of a larval cestode proteinase inhibitor, exhibited a marked suppression of proliferation when stimulated with Con A, PHA, PWM and ovalbumin. Reduced responsiveness was observed over a full range of concentrations of Con A (16-fold), PHA (50-fold), PWM (four-fold) and ovalbumin (16-fold). These results indicated that the inhibitory action could not be overcome by increasing the mitogen or antigen doses beyond optimal levels. This suppressive effect disappeared when the Taenia taeniaeformis proteinase inhibitor was added 20 h after the initiation of culture, suggesting that the inhibitor affects lymphocyte blastogenesis during the early stages of lymphocyte activation.

Animals↗
PubMed1983

Chemiluminescence response of equine alveolar macrophages during stimulation with latex beads, or IgG-opsonized sheep red blood cells.

Isolated equine alveolar macrophages were shown to generate a luminol-dependent light response when challenged with a phagocytic stimulus. The chemiluminescent response was not detected with luminol prepared at 1.0 x 10(-5) or 1.0 x 10(-4) molar concentrations, but was readily quantitated when used at a 1.0 x 10(-3) molar concentration. Challenge of the alveolar macrophages with latex particles or with equine IgG-coated sheep red blood cells elicited the luminol-dependent light response, whereas unchallenged equine alveolar macrophages or those challenged with unopsonized erythrocytes failed to emit light above background levels. Latex-bead-challenged macrophages released 8.06 times the total amount of light as those equine alveolar macrophages challenged with equine IgG-opsonized erythrocytes. This study represents the first investigation on chemiluminescence and equine alveolar macrophages.

Animals↗
PubMed1983

Surface receptors for IgG and complement on equine alveolar macrophages.

Isolated equine alveolar macrophages obtained by bronchopulmonary lavage of four live ponies demonstrated surface receptors for equine IgG, equine IgM, and complement-coated sheep red blood cells, but not equine IgM or complement-coated erythrocytes alone. In addition, demonstration of IgG receptors was found to depend on the level of erythrocyte sensitization and could not be demonstrated by red blood cell rosetting techniques at low levels of sensitization. Demonstration of receptors for equine complement by red cell rosetting techniques required the presence of both IgM antibody and serum derived (complement) components. This is the first such study of receptors on equine alveolar macrophages.

Animals↗
PubMed1983

Aggregation of equine platelets by PAF (platelet-activating factor).

Platelet-activating factor (PAF), a lipid released as a result of immediate allergic reactions from basophils and mast cells as well as by a variety of other cell types and stimuli, is one of the most potent platelet agonists and hypotensive agents known. Equine platelets stimulated over a wide range of PAF concentrations aggregated in a time- and dose-dependent manner. Maximum aggregation was observed at concentrations of PAF as low as 3.58 x 10(-14) M with platelet-rich plasma (PRP) and 3.58 x 10(-16) M with washed platelets. Furthermore, the aggregation observed did not appear to be breed-dependent. Finally, the platelet arachidonate pathway appeared to play no role in PAF-induced aggregation as exogenous arachidonate did not enhance the reaction, nor were equine platelets pretreated with 38 microM aspirin inhibited in their response to PAF. This level of aspirin totally inhibited the equine platelet aggregation response to arachidonate.

Animals↗
PubMed1983

Thromboxane A2 generation by the larval cestode, Taenia taeniaeformis.

The larval stage of the tapeworm, Taenia taeniaeformis, was incubated in different concentrations of arachidonic acid. At various times after incubation, aliquots were removed for bioassay on either 38 microM aspirin or non-aspirin-treated equine platelets and by radioimmunoassay for the thromboxane A2 breakdown product, thromboxane B2 (TXB2). Platelet agonist activity was detected as early as 30 sec after addition of the arachidonic acid. In aspirin-treated platelets, this agonist activity peaked at 1 to 4 min and thereafter decayed rapidly with a time course that was both worm and arachidonic acid dependent. When assayed on non-aspirin-treated platelets the agonist activity was again detectable as early as 30 sec after addition of arachidonic acid, peaked at 1 to 3 min and then decayed very slowly over a 30-min period of incubation. It was found that levels of TXB2 were detected which increased over time concomitant with the decay of the platelet agonist activity. The most consistent detection of TXB2 generation was at 30 min with a mean of 49.6 pg and a range of 22.1 to 84.8 pg for four experiments. This report presents the first evidence for arachidonic acid utilization by a cestode or trematode and could in part provide an explanation for the marked cellular inflammation noted around dead or dying parasites.

Animals↗
PubMed1983

PGE2 generation and release by the larval stage of the cestode, taenia taeniaeformis.

The existence of an arachidonate cascade in invertebrate species has been little explored. We therefore sought to determine if two important prostanoid compounds, PGE2 and prostacyclin, PGI2 were generated and released by the larval stage of the cat tapeworm, Taenia taeniaeformis. PGE2 and PGI2 were identified by specific radioimmunoassay after thin layer chromatography of chloroform/methanol extracts of the worms or in vitro saline culture media. We detected a release of 176-182 pg of PGE2 from 2 worms after a 60' incubation at 37 degrees C with 4.5 mM exogenous sodium arachidonate. No release of PGI2 was detected immunochemically although 41 pg of immunoreactive material was identified in chloroform/methanol extracts of the worm alone. We therefore suggest that modulation of host immune responses could occur by the generation and release of prostanoid compounds such as PGE2, lipids which markedly suppress host cellular reactivity to the parasite. Secondly, the lack of any clot formation around the living organism may well reflect PGI2 presence at the surface of the parasite membrane. Although these findings are at present limited to larval cestodes we would propose that they may be more general means of evading host responses than heretofore suspected.

Animals↗
PubMed1983

Aggregation of equine platelets by Onchocerca cervicalis collagen.

The arachidonic acid pathway plays an important role in many inflammatory reactions. Current evidence suggests that platelets can play a central part in host inflammation. Since microfilariae are mobilized into the bloodstream following diethylcarbamazine (DEC) treatment, we have studied the effects of Onchocerca cervicalis cuticle preparations on equine platelet aggregation. The authors have found that O cervicalis cuticular preparations can induce platelet aggregation in vitro. Furthermore, this activity was abrogated by treatment with collagenase and not hyaluronidase, elastase, or alpha-chymotrypsin. When this evidence is viewed collectively with the evidence for in vivo parasite cuticular damage following DEC treatment, it becomes entirely plausible that the cuticular damage may indeed reveal a platelet-reactive surface, thus permitting platelet-parasite binding to occur. This binding would result in platelet aggregation and the generation and release of platelet-derived arachidonate metabolites. These metabolites may play a very critical role in the development of the described pathologic sequelae observed following DEC treatment. Field studies using cyclooxygenase and lipoxygenase inhibitors might therefore be very efficacious in decreasing the frequency of side effects due to DEC or other potentially effective drug regimens.

Adenine↗
PubMed1983

Modulation of equine platelet function by diethylcarbamazine (DEC).

Equine platelets, when treated with the anthelmintic drug diethylcarbamazine (DEC), gave a dose-dependent release of radiolabeled serotonin without concomitant aggregation. At levels of the drug that gave only minimal release of radiolabel, marked dose-dependent inhibition of platelet aggregation to three of four platelet agonists tested--adenosine diphosphate (ADP), collagen, and arachidonic acid--was observed. With ADP, inhibition was observed to be reversed by removal of DEC prior to agonist challenge. However, with collagen, inhibition was only partially reduced by prior removal of DEC; whereas with arachidonate the DEC inhibition appeared not to be reduced by removal of the drug. Thrombin-induced aggregation was not inhibited by DEC. DEC therefore has the heretofore unrecognized property of modulating platelet function to several platelet agonists as well as inducing the platelet release of serotonin. Our results would suggest a reversible membrane-drug interaction as the potential site of modulation for ADP and collagen, whereas an apparent irreversible inhibition is suggested for arachidonate-induced aggregation.

Adenosine Diphosphate↗