Biomedical subjects

A G Bentley

Publications and source records attributed to A G Bentley.

11 recordsLinked to original sources

PubMed1986

In vitro granuloma formation using defined antigenic nidi.

The in vitro granuloma model provides an excellent tool to study granulomatous hypersensitivity. In our studies of granuloma formation in schistosomiasis, we have demonstrated the utility of the model with respect to analysis of human PBL responses, cloned T cells, purified antigens of the parasite, and regulatory mechanisms. We have also presented data which demonstrate the applicability of this model to other antigenic systems. While the suggestion that this model may be suitable for the study of sarcoidosis may be premature, we would propose that the system may be adapted to screen potentially causative antigens. Furthermore, with the identification of the critical antigen(s), the in vitro granuloma model will facilitate studies at the clinical level.

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PubMed1985

In vitro delayed hypersensitivity granuloma formation: development of an antigen-coated bead model.

Previously, we have described an in vitro model of granulomatous hypersensitivity around Schistosoma mansoni eggs in both the murine model of schistosomiasis and in human schistosomiasis. These studies describe a new model of in vitro granuloma formation that complexes soluble egg antigen from S. mansoni eggs, a partially purified protein derivative of Mycobacterium tuberculosis (PPD), or bovine serum albumin to carrier beads. Ultrastructural and morphologic evaluations demonstrate that there are initial macrophage interactions, followed by the recruitment of antigen-specific T cells that interact with and recruit macrophages, lymphocytes, granulocytes, and fibroblasts. Finally, there is a stage of granulomatous organization involving fibroblast proliferation and collagen deposition. The in vitro reactivity, defined by a quantitative granuloma index, correlates with in vivo granulomas around S. mansoni eggs in the livers of infected cell donor animals. In vitro granuloma formation against PPD-coated beads correlated with delayed cutaneous hypersensitivity against PPD, which was judged by footpad swelling. The reactions demonstrate antigenic specificity and were intrinsically modulated in a manner that is analogous to that previously shown with the in vitro egg granuloma model. This model of in vitro granuloma formation promises to be a useful tool for elucidating mechanisms of cellular immunity and regulation.

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PubMed1985

Response of the medullary thick ascending limb to hypothyroidism in the rat.

Hypothyroidism in the rat is associated with a decrease in kidney size and weight. We have shown previously that this decrease involves all nephron segments in the cortex and outer medulla and is especially pronounced in the medullary thick ascending limb (mTAL). Therefore, the present study was undertaken for examination of the effect of hypothyroidism on the ultrastructure of the rat mTAL. Hypothyroidism was induced by feeding aminotriazole (ATZ), 0.5 g/kg of food, for 4 weeks. A second group of animals received ATZ plus a daily injection of L-thyroxine (T4). A third group was fed a normal diet only and served as control animals. The kidneys were preserved by in vivo perfusion with 3% glutaraldehyde, and tissue from the inner and outer stripe of the outer medulla was processed for electron microscopy. Morphometric analysis revealed a significant decrease in the cross-sectional area of the mTAL in both the inner and outer stripe of the outer medulla in hypothyroid animals. No changes were observed in the surface density of either the apical or basolateral plasma membranes following ATZ treatment. However, when calculated per millimeter tubule, there was a significant decrease in the surface area (SL) of both the apical and basolateral plasma membranes of the mTAL of hypothyroid animals in comparison with control animals. Simultaneous treatment with T4 prevented the ATZ-induced reduction in both tubule cross-sectional area and in the SL of the plasma membrane. These findings suggest that the observed changes in SL of the plasma membrane of the mTAL are due to a regulatory role of thyroid hormone in membrane proliferation as well as in cell growth in general.

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PubMed1984

The histology and ultrastructure of the Meyers-Kouwenaar body in ferrets infected with Brugia malayi.

A study was made of the Meyers-Kouwenaar (MK) body in the livers of experimentally infected ferrets. Meyers-Kouwenaar bodies, the carcasses of microfilariae (mff) covered by deposits of Splendore-Hoeppli (SH) material, were found in small abscesses of eosinophils and in granulomas. The SH deposits varied from an eosinophilic, hyaline fringe around intact mff to multilayered deposits surrounding an unrecognizable granular remnant. In abscesses, peroxidase activity was intense in SH deposits and the surrounding eosinophils. The presence and localization of IgG were variable in MK bodies, as detected by an enzyme-linked immunohistologic assay; and antigens of mff were not detected in the SH deposits. Electron microscopy of the MK body demonstrated a layered, radial deposition of amorphous and granular material on the mff and a structural heterogeneity which apparently included leukocyte granules and other cell organelles. Leukocytes surrounding MK bodies in abscesses were often degranulated and degenerate; incorporation of lysosomes of eosinophils and cellular debris into the SH deposits at the periphery of the MK bodies was indicated.

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PubMed1983

The immunologic response of congenitally athymic rats to Schistosoma mansoni infection. I. In vivo studies of resistance.

The responses of congenitally athymic (Nu/Nu) rats to an initial exposure and to re-exposure to Schistosoma mansoni were compared to those manifested by thymic reconstituted (Nu/Nu*TxR), heterozygous littermate controls (Nu/+) and the highly characterized Fischer rat strain. Congenitally athymic rats rejected the developing worms of an initial infection more slowly than did thymic reconstituted or heterozygous animals. These latter responses were highly comparable to those demonstrated by the Fischer rat. In addition, the congenitally athymic rats manifested lower peripheral blood eosinophilia in response to infection. Resistance to reinfection in athymic animals was impaired and associated with a decreased immunoinflammatory histologic response to hepatic intravascular parasites and to eggs lodged in the hepatic vasculature. There was little evidence of inflammatory responses involving degranulating eosinophils, lymphocytes, or macrophages in the athymic rats. Finally, athymic animals produced antibody that was less capable of passively transferring resistance in adoptive-challenge experiments; however, antibody produced in heterozygous animals conferred significant resistance when adoptively transferred to athymic animals. These results suggest that resistance to initial and subsequent challenge by S. mansoni infections in the rat is highly reliant upon T-dependent mechanisms that result in the production of antibody-dependent, possibly cell-mediated resistance. Additional studies utilizing in vitro analysis of a variety of antibody functions to define the mechanisms of T-dependent immunologic resistance in the congenitally athymic rat are the subject of the accompanying manuscript.

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PubMed1983

Schistosoma mansoni: morphologic changes induced by maintenance in vitro.

Adults of Schistosoma mansoni were incubated in several culture media at various time intervals ranging from 2 to 96 hr. The morphologic changes induced by the incubation were documented using both scanning and transmission electron microscopy. These included changes in the tegument, esophageal cells, and cecum. Variability was noted among worms within experimental groups and the surface changes on single worms were frequently observed to have patchy distribution. Based on morphologic changes observed, culture media were ranked as adequate, mediocre, or inadequate. RPMI-1640 + 50% fetal calf serum, Eagle's MEM with Earle's salts (no serum), and McCoy's 5A Medium + serum were judged adequate. Basal Eagle's Medium, Triple Eagle Medium, NCTC-135, and Earle's Balanced Salt Solution (all with or without serum) were judged mediocre. Hanks' Basal Salt Solution (with or without serum) was judged as severely inadequate. All media tested gave better results in the presence of serum. These factors point to the necessity for the use of carefully selected culture media, as well as adequate controls and sampling techniques in the interpretation of in vitro experiments with S. mansoni.

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PubMed1983

Schistosoma mansoni: evaluation of selected preparative procedures for transmission and scanning electron microscopy.

Evaluation of numerous procedures for collection and preparation of Schistosoma mansoni for scanning (SEM) and transmission microscopy (TEM) revealed that some commonly used methods result in introduction of osmotic or mechanical damage. Modification and selection of appropriate procedures allowed elimination of these artifacts. Not eliminated by these procedures, however, were several kinds of spheres and blebs that were either external to the apical plasma membrane of the tegument or budding from it. After careful examination of all procedures, we concluded that these spheres appear to some extent on all schistosomes prepared for either SEM or TEM and may represent either a normal component of the schistosome surface, a constant host contaminant, or an artifact not eliminated by any of the multiple modifications of technique examined.

Anesthetics↗

PubMed1982

Ultrastructural analysis of the cellular response to Schistosoma mansoni. III. The in vitro granuloma.

The in vitro formation of the Schistosoma mansoni egg granuloma was examined using transmission and scanning electron microscopy and functional assay of isolated cell populations. This analysis has defined those cells which contribute to the evolution of the granulomatous reaction. Development of the granuloma is analogous to the in vivo process consisting of (1) initial response by macrophages and T lymphocytes, (2) subsequent recruitment of numerous macrophages, lymphocytes, eosinophils, and fibroblasts and, finally, (3) production and deposition of collagen leading to fibrosis in the granuloma. Documentation that formation of the in vitro granuloma closely recapitulates the in vivo process further confirms the potential usefulness of this model in analyzing the physiologic and immunologic mechanisms involved in granulomatous hypersensitivity and fibrosis.

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PubMed1981

Ultrastructural analysis of the cellular response to Schistosoma mansoni: initial and challenge infections in the rat.

Morphological examination of both the lung and liver stages of Schistosoma mansoni infection in the CDF rat was conducted to further define the interactions of host cells with developing schistosomula. Examination of the developing schistosomula in the lungs revealed that all worms observed were in the vasculature, usually wedged in a vessel just large enough to accommodate the worms and a few erythrocytes. No concentrations of granulocytes or mononuclear cells were seen in direct contact with worms. Examination of livers 17-19 days postinfection showed a similar intravascular location for the worms. There was a striking perivascular response in the livers of infected rats, consisting of numerous eosinophils, frequent mast cells and macrophages, as well as mononuclear cells. No cells from this response were observed in direct contact with the schistosomula. In challenge exposures, the portal venules containing schistosomula were surrounded by an intense perivascular accumulation of eosinophils, macrophages, mast cells, and plasma cells. Fibroblasts and intercellular deposition of collagen in the inflammatory focus were also evident. Granulocytes, primarily eosinophils, were observed in the blood spaces near the schistosomula. This secondary cellular response differed from the initial hepatic lesion in containing increased numbers of mast cells and plasma cells, and in the presence of perivascular fibrosis.

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PubMed1981

Ultrastructural analysis of the cellular response to Schistosoma mansoni. II. Inflammatory response in rodent skin.

A significant proportion of Schistosoma mansoni schistosomula die soon after penetration of mammalian host skin. This study was conducted to further define the host cellular response which occurs in the skin and which may contribute to early schistosomulum death in the resistant CDF rat and the more susceptible BALB/c mouse. In primary abdominal skin exposures of both hosts the initial 6-hour response is marked edema and epidermal cell disruption in the schistosomulum penetration tracts accompanied by migration of neutrophils to surround the parasites and into damaged areas of the epidermis and dermis. Challenge exposures in previously infected hosts result in more intense exudative inflammation than is observed in initial exposures with the additional infiltration of eosinophils into the dermis and epidermis. Mast cells are numerous and are occasionally observed degranulating. By 24 hours following either initial or challenge exposures the infiltration of granulocytes is more intense. Focal areas of neutrophils, eosinophils, and necrotic cells are frequent in the epidermis. Postcapillary venules contain large numbers of granulocytes. The vascular endothelium is frequently vacuolated and occasionally exhibits focal degeneration. Rat hosts show responses which are qualitatively similar to those in mouse hosts but quantitatively more intense. Smaller numbers of eosinophils were observed in the immune mouse at 24 hours than have been reported in previous studies. This may be attributable to differences in strain, in the time course of response in abdominal as compared with ear skin, or in the levels of immunity in the animals used.

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PubMed1980

The immunologic modulation of morbidity in schistosomiasis. Studies in athymic mice and in vitro granuloma formation.

These studies were designated to test the hypothesis that granulomatous hypersensitivity associated with schistosomiasis, its modulation, and subsequent morbidity are contingent on thymic-dependent lymphocyte function. Studies in athymic mice were integrated with in vitro studies on granuloma formation. Athymic animals tolerate low levels of infection well but are increasingly susceptible to morbidity as the challenge burden increases or becomes associated with simultaneous additional stress such as bacterial infection. In addition, the athymic animals produce smaller granulomas and fail to demonstrate accelerated granuloma formation, the spontaneous modulation of granulomas, or significant resistance to reinfection. These deficiencies could be reversed by thymic reconstitution. In vitro studies indicate that the response to egg antigens was due to the interaction of two subpopulations of T lymphocytes. Studies of "in vitro granuloma formation" augmented the in vivo findings, suggesting that the "in vitro granuloma" represents an excellent analog for delayed hypersensitivities; granuloma production was contingent on a macrophage function and a specific subpopulation of T lymphocytes defined as Ly1+. Granuloma modulation was due to two mechanisms, one contingent on direct suppression by ly2,3+ cells and the other by feedback inhibition requiring Ly,2,3+ cells. These studies suggest the feasibility of combined in vivo and in vitro technology to study the mechanisms of granuloma formation and subsequent morbidity.

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