Search PubMed⌕ Search

Biomedical subjects

R Burger

Publications and source records attributed to R Burger.

At least 109 records · Page 6Linked to original sources

Major histocompatibility complex restriction of T-cell responses to varicella-zoster virus in guinea pigs.

Varicella-zoster virus (VZV), adapted to grow in guinea pig fibroblasts, was injected subcutaneously into Hartley, strain 2, and strain 13 guinea pigs. Serum immunoglobulin G antibodies were detected 2 weeks later, and T-cell proliferative responses by blood lymphocytes were found 3 weeks after injection. The proliferating cells bound the 155 antibody, which defines a CD4-like subset of guinea pig T lymphocytes. VZV-infected fibroblasts of human, Hartley, and strain 13 origin elicited equivalent amounts of proliferation, which was quantitatively greater than that obtained with an extracted VZV antigen. Uninfected (control) human or guinea pig fibroblasts did not elicit T-cell proliferation. The proliferative response to VZV required the presence of autologous (strain 2 or 13) antigen-presenting cells and was blocked by the addition of an anti-class II major histocompatibility complex antibody. Effector cells obtained from in vitro cultures mediated class II-restricted cytotoxicity to L2C cells incubated with VZV. Class I-restricted responses were obtained only by cross-priming strain 2 animals with strain 13 peritoneal exudate cells which had been preincubated with VZV. The data indicate that guinea pigs resemble humans in that class II-restricted T cells with specificity for VZV are more readily cultured from blood than are class I-restricted cells.

Animals↗

Pulmonary hypertension after postlavage lung injury in rabbits: possible role of polymorphonuclear leukocytes.

Previous studies showed that repeated lung lavage leads to a severe lung injury with very poor gas exchange, a substantial protein leak into the alveoli with hyaline membrane formation, pulmonary hypertension, and migration of granulocytes (PMN) into the alveolar spaces. Depletion of PMN leads to a better gas exchange and a markedly decreased protein leak with only scanty hyaline membranes. In this study we show that there is sustained pulmonary hypertension after the lung lavage, but in PMN-depleted rabbits there is no postlavage increase in pulmonary arterial pressure. Changing the shunt fraction by manipulating mean airway pressure still leads to a hypoxic vasoconstriction with increase of pulmonary arterial pressure. Thus, after lung lavage, pulmonary reactivity to hypoxia is still preserved. Comparisons between high-frequency ventilation and conventional mechanical ventilation at the same mean airway pressures showed that equal mean airway pressure in these two very different modes of ventilation do not translate into the same mean functional lung volumes.

Animals↗

Identification and functional characterization of guinea-pig CD4: antibody binding transduces a negative signal on T-cell activation.

The guinea-pig (gp) CD4 protein was identified using the rat monoclonal antibody (mAb) H155 derived from an interspecies hybrid. The hybrid was obtained after immunization of rats with purified guinea-pig T lymphocytes and fusion to a mouse myeloma line. The mAb H155 reacted with a subpopulation (60-70%) of nylon-wool-purified guinea-pig T cells. The majority of thymocytes also expressed the H155 antigen. Immunohistological staining showed that predominantly the cortical thymocytes were H155-positive, whereas a part of the medullary cells did not express the antigen. After cell-surface radioiodination of T cell lines, the mAb H155 immunoprecipitated a molecule of about 55,000 MW both under reducing and non-reducing conditions. The antigen recognized by mAb H155 on guinea-pig T cells resembles the human or mouse CD4 antigen. Depletion experiments in combination with functional studies further supported this assumption. In proliferation assays mAb H155 inhibited T-cell responses in vitro. Both the antigen- and alloantigen-induced T-cell activation were impaired in the continuous presence of mAb H155. In addition, mAb H155 inhibited both the mitogen-induced T-cell activation and T-cell proliferation induced by mitogenic mAb and phorbol myristate acetate (PMA). Binding of the mAb H155 to the CD4 molecule might therefore transduce a negative signal on T-cell activation.

Animals↗

C3 deficiencies.

Explore the source record for details and available documents.

Animals↗

Reflection of changes in membrane constituents in various regions of Alzheimer brains to differential scanning thermograms.

To test whether changes in basic biochemical membrane constituents were reflected in membrane fluidity measurements, protein, total lipids, triglycerides, lecithin, cholesterol and alkaline phosphatase were determined in frontal cortex, hippocampus, putamen and nucleus basalis Meynert (NbM) of DAT brains and controls and compared to differential scanning thermograms. Biochemical changes were most pronounced in the hippocampus, while thermostability was altered in the NbM and the frontal cortex. The results indicate that changes in protein content, but not in lipid composition were reflected in alterations of thermostability of the brain regions examined.

Aged↗

Brainstem lesion revealed by MRI in a case of Leigh's disease with respiratory failure.

This 6-year-old girl was admitted with insufficient involuntary breathing and generalized hypotonia. T2-weighted MR images showed bilateral symmetrical tubular hyperintense lesions in the medio-caudal part of the medulla oblongata that correlated well with demyelination and gliosis in the regions of the reticular formation and the nucleus solitarius found at autopsy. The typical lesions of Leigh's disease in the basal ganglia were not present, which made the diagnosis uncertain prior to the histopathological findings. MRI was very helpful in deciding on further management of the patient.

Brain Diseases, Metabolic↗

Tumor infiltrating leukocytes (tils) during progressive tumor growth and BCG-mediated tumor regression.

Tumor regression was induced by intralesional injection with BCG, 7 days after inoculation of line 10 hepatocellular carcinoma cells into strain 2 guinea pigs. Tumor-infiltrating leukocytes (TILS) were characterized immunohistochemically with 11 monoclonal antibodies (MoAbs) during the induction phase of line 10-immunity, and during immune-mediated regression of the tumor, at days 12 and 28 after tumor cell inoculation, respectively. At day 5 after BCG-injection (day 12 after tumor cell inoculation), there were no major differences between the TIL subpopulations of the BCG-treated and untreated tumors. The TILS were mainly T-cells, as identified by MoAbs against Pan T-cells (CT5), T-cytotoxic/suppressor cells (CT6) and T-helper/inducer cells (H155). A limited number of macrophages was also present. However, at day 21 after BCG-treatment (28 days after tumor cell inoculation), the fibrous stroma was increased dramatically in most of the BCG-treated tumors, and as a result, the tumor cell islets were smaller than in control tumors. In the BCG treated tumors, the numbers of T-cells and macrophages were increased. In growing and regressing tumors, MHC class I and II antigens were strongly expressed in TILS and in the tumor stroma. Line 10 tumor cells prior to inoculation expressed no MHC class I or II antigens. In the centers of the tumor islets at days 12 and 28, expression of these antigens was not found. However, MHC class I and II antigens were expressed on tumor cells at sites where they lay close to the fibrous stroma or TILS. This observation was made in progressively growing tumors and was most apparent in BCG-treated tumors.

Animals↗

Structure, cellular distribution, and functional characteristics of the guinea pig leucocyte common antigen.

The guinea pig leucocyte common antigen (LCA), expressed on different hemopoietic cells, was examined using the monoclonal antibody (mAb) H 201. Immunohistology and FACS analysis revealed that T and B lymphocytes, macrophages, and thymocytes express the H 201 epitope in comparable density. The level of LCA-expression increased during the course of maturation and activation of T cells. Differences in the molecular weight of LCA were observed, which depended on the nature of various cell populations, indicating that in each case alternative variants of LCA are expressed. The molecular weight of guinea pig LCA ranged from 175 kDa on thymocytes, up to a 230-kDa variant found on B lymphocytes. Antigen- or alloantigen-induced T cell activation in vitro was moderately affected by the continuous presence of mAb 201. In contrast, the PHA-mediated T cell proliferation was strongly and selectively enhanced, supporting the assumption of an LCA involvement in the "alternative pathway" of T cell activation.

Animals↗

Transcutaneous carbon dioxide pressure for monitoring patients with severe croup.

In a prospective investigation of 17 children with severe croup, we analyzed the effect of epinephrine inhalations and mild sedation with chloral hydrate on transcutaneous carbon dioxide pressure (tcPCO2), pulse oximetry measurements, and croup scores. There was a highly significant reduction (p less than 0.001) in the tcPCO2 values and croup scores after inhalation of epinephrine. The changes in the tcPCO2 values correlated with the clinical findings. Mild sedation also significantly improved the croup scores but failed to influence the tcPCO2 values. There was not statistically significant difference in pulse oximetry saturation, fraction of administered oxygen, heart rate, or respiratory rate before and after inhalation of epinephrine or chloral hydrate administration. Monitoring tcPCO2 appears to be a reliable and objective tool for managing patients with upper airway obstruction, whereas croup scores may be misleading.

Blood Gas Monitoring, Transcutaneous↗

Phototoxic erythema following PUVA treatment: independence of complement.

The effect of PUVA treatment on normal human serum (NHS), on isolated PMN, or on C3-deficient guinea pigs and congenic (C3-competent) control animals was tested. At a concentration of 0.1 or 1 mM/l 8-MOP and UVA doses of 5-30 J/cm2, PUVA failed to induce any detectable C3-cleavage in NHS. Furthermore, when the complement (C) activation in NHS had been induced before or after PUVA treatment by various methods. PUVA did not modulate the extent of C3-cleavage. PUVA did not affect the viability of isolated PMN, nor did it induce a release of LDH or elastase. No differences between C3-deficient and C-competent guinea pig skin exposed to PUVA were observed in erythema or histologic responses. Immunohistologic examination of specimens from normal guinea pigs revealed C3b and C3d deposits on necrotic keratinocytes, findings restricted to the PUVA-treated areas. Necrosis of keratinocytes was present in skin specimens of C3-deficient animals from PUVA-treated sites to a similar extent. However, deposits of C3-related antigens were completely absent there. From these observations, we suggest that the induction of phototoxic erythema following PUVA treatment is independent of complement.

Animals↗

Lung injury in a surfactant-deficient lung is modified by indomethacin.

Repetitive total lung lavage in adult rabbits leads to a reproducible severe surfactant-deficient lung injury. Hypoxemia requiring mechanical ventilation occurs, accompanied by a substantial pulmonary hypertension, a large intra-alveolar protein leak, peripheral neutropenia, and pathological features of marked neutrophil infiltration with extensive hyaline membrane formation. Pretreatment with indomethacin abolishes postlavage pulmonary hypertension, preserves a slightly better lung function with higher arterial PO2, and prevents the postlavage peripheral neutropenia found in untreated animals. Pretreatment with a thromboxane A2 receptor blocker (L 655,240, Merck Frosst, Canada) also completely attenuated pulmonary hypertension, providing evidence that thromboxane A2 mediates pulmonary arterial hypertension after lung lavage. However, specific thromboxane receptor blockade had no other long-lasting beneficial effects on the ongoing injury in this model.

Animals↗

Molecular basis of complement C3 deficiency in guinea pigs.

In experiments to ascertain the biochemical basis of a genetically determined deficiency of the third component of complement (C3) in guinea pigs, we found that C3-deficient liver and peritoneal macrophages contain C3 messenger RNA of normal size (approximately 5 kb) and amounts, that this mRNA programs synthesis of pro-C3 in oocytes primed with liver RNA and in primary macrophage cultures. In each instance, heterodimeric native C3 protein was secreted with normal kinetics but the C3 protein product of the deficient cells failed to undergo autolytic cleavage and was unusually susceptible to proteolysis. These data and a selective failure of C3 in plasma of deficient animals to incorporate [14C]methylamine suggested either a mutation in primary structure of the C3 protein or a selective defect in co- or postsynthetic processing affecting the thiolester bridge, a structure important for C3 function. A mutation in the primary structure of C3 was ruled out by comparison of direct sequence analysis of C3 cDNA generated from two C3 deficient and two C3 sufficient guinea pig liver libraries. Three base pair differences, none resulting in derived amino acid sequence differences were identified. Finally, restriction fragment length polymorphisms were identified in the C3 gene that are independent of the deficiency phenotype. This marker of the C3 gene permits testing of these hypotheses using molecular biological and classical genetic methods.

Amino Acid Sequence↗

Quantitation of the anaphylatoxin C3a in the presence of C3 by a novel sandwich ELISA using monoclonal antibody to a C3a neoepitope.

C3a levels in plasma are usually measured by a competitive inhibition radioimmunoassay (RIA) using 125I-labelled C3a-desArg and antibodies to C3a capable of detecting C3a determinants which are also present on the native C3. Therefore, prior to the assay native, non-cleaved C3 has to be removed completely from the C3a-containing sample by precipitation. We developed a new rapid two-site sandwich ELISA system for the quantitation of C3a-desArg in plasma. This immunoassay uses a monoclonal antibody (mAb H466) reacting with C3a-desArg but not with C3. The reactivity of mAb H466 with a neoantigenic determinant of C3a-desArg permitted the direct quantitation of C3a-desArg without removal of C3 from the sample. The mAb H466 was used as a capture antibody and bound C3a-desArg was detected with a second peroxidase-labelled anti-C3a mAb. The lower limit of detection of C3a-desArg in this ELISA was 1 ng/ml. The C3a-desArg levels measured in the plasma samples of various patients were found to differ over a wide range. A good correlation was observed between the results obtained in the RIA and those obtained in the ELISA (r = 0.95). High levels of C3a-desArg were detected in plasma from patients with multiple trauma and patients undergoing haemodialysis. The C3a-desArg assay described should facilitate the routine quantitation of C3a in samples of plasma.

Antibodies, Monoclonal↗

Analysis of guinea pig leukocyte antigens using interspecies T cell hybrids.

In the guinea pig system, there are no T lymphocyte tumors available. In addition, in this species the production of T cell lines in vitro for analysis of T cell markers or function proved to be difficult. As an alternative approach, guinea pig X mouse and guinea pig X rat T cell hybridomas were obtained by fusion of guinea pig T cells with HAT-sensitive mouse or rat thymomas. In ten fusions a total of 578 hybrids were produced and kept in culture for periods ranging from weeks up to several months. The highest yield was obtained when the Mb C 12 line was used as tumor parent. BW 5147 and the rat thymoma W/Fu(C58NT)D gave slightly lower fusion efficiencies. The yield depended also on the pretreatment of the parental cells. Activation by MLR proved to be most effective. A number of interspecies hybrids expressed guinea pig T cell differentiation antigens as detected by a cell ELISA. The positive hybrids were recloned several times and exhibited a stable expression of these markers, even after continuous culture for more than 2 months. Western blot analysis was used to confirm antigen expression at the protein level by comparing the hybrids with both parental cells. The hybrids expressed the proteins of the guinea pig lineage. No reaction was observed with the murine or rat thymomas. Therefore, the application of interspecies T cell hybrids provides an alternative for studies of guinea pig T cells. The cells are easy to grow and to clone and may be stored frozen in liquid nitrogen. The hybrids should permit analysis at the clonal level also for functional studies.

Animals↗

Echinococcus multilocularis: in vitro secretion of antigen by hybridomas from metacestode germinal cells and murine tumor cells.

Hybrid cells were produced from Echinococcus multilocularis metacestode germinal cells and murine tumor cells. Small colonies were formed which, while ceasing to grow after a few generations, remained viable for at least 10 weeks. These hybridoma cells secrete antigen(s) reacting in indirect immunofluorescence and ELISA specifically with sera from patients suffering from an E. multilocularis infection. The antigen(s) appear suitable for the differential diagnosis of E. multilocularis and E. granulosus. Thus, hybridoma cells may produce helminth antigens.

Animals↗