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Biomedical subjects

M Troxler

Publications and source records attributed to M Troxler.

13 recordsLinked to original sources
PubMed2005

Ischaemic skeletal muscle increases serum ischaemia modified albumin.

OBJECTIVES: Ischaemia modified albumin (IMA) has been used as a marker of myocardial ischaemia but little is known about its production during ischaemia of other tissues. The clinical models of patients with intermittent claudication and major arterial surgery were used to investigate IMA production from ischaemic skeletal muscle. DESIGN: Prospective clinical study. MATERIALS AND METHODS: IMA was measured pre-operatively, at end ischaemia, and 5 min, 4, 24, 48, 72 and 144 h post-surgery in patients undergoing (a) revascularisation for intermittent claudication (IC, n=15), (b) abdominal aortic aneurysm repair (AAA, n=12) and controls (n=16). RESULTS: The median pre-operative IMA concentration in IC patients was significantly higher than the AAA group (88.3 versus 83.5 U/ml, p=0.036) and controls (88.3 versus 80.3 U/ml, p=0.031). IMA concentrations increased significantly during arterial clamping in both IC and AAA groups (88.3 versus 120.0 U/ml, p=0.001; 83.5 versus 118.8 U/ml, p=0.002, respectively) consistent with increased skeletal muscle ischaemia. In contrast, there was only a mild perioperative increase in the controls (80.3 versus 91.6 U/ml, p=0.012). CONCLUSIONS: Patients with intermittent claudication have significantly elevated IMA and skeletal muscle ischaemia during arterial surgery results in significantly increased circulating IMA. When IMA is used to detect myocardial ischaemia, ischaemic skeletal muscle must be excluded.

Adult↗
PubMed2004

Increased nitrotyrosine production in patients undergoing abdominal aortic aneurysm repair.

BACKGROUND: Vascular inflammation is implicated in the pathogenesis of atherosclerosis and abdominal aortic aneurysm (AAA), and is thought to involve reactive species such as the nitric oxide-derived oxidant peroxynitrite. In the present study nitrotyrosine was measured as a stable marker of peroxynitrite production in vivo. METHODS: Perioperative blood samples were obtained from patients undergoing elective open or endovascular repair of an AAA and from patients with intermittent claudication, smoking aged-matched controls, non-smoking aged-matched controls and non-smoking young healthy controls. Plasma nitrotyrosine was measured by an enzyme-linked immunosorbent assay. RESULTS: The median plasma nitrotyrosine concentration in patients with an AAA (0.46 nmol nitrated bovine serum albumin equivalents per mg protein) was significantly higher than that in patients with intermittent claudication (0.35 nmol; P = 0.002), smoking controls (0.36 nmol; P = 0.001), non-smoking controls (0.35 nmol; P = 0.002) and young healthy controls (0.27 nmol; P < 0.001). Nitrotyrosine concentrations increased during early reperfusion in open AAA repair, but not during endovascular repair. AAA exclusion from the circulation reduced levels to control values (P = 0.001). CONCLUSION: Patients with an AAA had raised levels of circulating nitrated proteins compared with patients with claudication and controls, suggesting a greater degree of ongoing inflammation that was not related to smoking.

Adult↗
PubMed2001

Penetrating atherosclerotic ulcers of the aorta.

BACKGROUND: Penetrating aortic ulcers burrow into the aortic wall and can have fatal consequences. Although they were first described as long ago as 1934 they have only recently been recognized as a distinct pathological entity. METHOD: A review of the current literature was undertaken, based primarily on an English language Medline search with secondary references obtained from key articles. RESULTS: Penetrating aortic ulcer is principally a disease of elderly hypertensive men. It may run a benign course or may produce complications such as aortic rupture, embolization and aneurysm formation. Presentation may be identical to that of classical aortic dissection, but the distinction is important because an ulcer may be more likely to cause rupture. CONCLUSION: Open surgical repair has been the 'gold standard' of treatment but endovascular stenting is an attractive option in this group of frail patients.

Aortic Aneurysm↗
PubMed1994

Light and electron microscopic in situ hybridization: non-radioactive labeling and detection, double hybridization, and combined hybridization-immunocytochemistry.

We performed light and electron microscopic in situ hybridization, according to the same protocol and without pretreatment of sections, on Lowicryl- and LR Gold-embedded cells. Digoxigenin (DIG)- or biotin-labeled riboprobes were visualized by direct or indirect immunodetection using commercially available gold-antibody conjugates with 0.8-10-nm gold grains. At the ultrastructural level, the main findings were that DIG-labeled probes gave a slightly higher labeling intensity (grains per signal) than biotin. The direct detection method produced a more compact signal, which led to better resolution at medium and high magnifications. Labeling intensities of all gold grain sizes were essentially equal. Grain sizes of 5 nm and larger were highly preferable because available enhancement methods are unsatisfactory for ultrasmall grains. The optimized immunodetection protocols are suitable for double hybridization with two different probes and for combined hybridization and immunocytochemistry.

Antibodies↗
PubMed1992

Intracellular localization of poliovirus RNA by in situ hybridization at the ultrastructural level using single-stranded riboprobes.

Polioviral RNA was localized by electron microscopic in situ hybridization on sections of poliovirus-infected HEp-2 cells. Viral plus-strand RNA was found accumulated in the close surroundings of the membrane-bound replication complex. Two different regions of the viral genome were detected with the same frequency, which indicates the predominant presence of full-length genomic RNA. Viral proteins of the P2 and the P3 genomic region were detected mainly over the core of the replication complex, whereas the hybridization signal was present rather at the peripheral parts of the complex. A more than 100-fold excess of viral plus- over minus-strand RNA was found by strand-specific hybridization to RNA extracted from isolated replication complexes. These findings support the idea of a pool of viral plus-strand RNA set free from the replication complex and accumulating in the close vicinity of the replication complex possibly before encapsidation.

Cells, Cultured↗
PubMed1992

Immunocytochemical localization of capsid-related particles in subcellular fractions of poliovirus-infected cells.

The structural proteins of poliovirus can assemble into a series of different configurations (capsid-related particles, CRP). Only some seem to be true capsid precursors and the role of most CRP in morphogenesis is unclear. We used electron microscopic immunocytochemistry with monoclonal antibodies recognizing different CRP [protomers, pentamers, 65S empty capsids (EC), 74S-EC, and virions] to locate CRP in subcellular fractions containing virus-induced vesicles associated with the viral replication complex. We found pentamer antigenic CRP to be associated with the replication complex. The same pentamer antigenicity was exhibited by novel, "capsid-like" structures attached to the surface of the virus-induced vesicles. Upon solubilization of the vesicular fraction, mainly 65S-EC and only negligible amounts of pentamers were found by sucrose gradient analysis and by immunoprecipitation. We show that the pentamer antigenic particles are converted into 65S-EC when their membranous support is dissolved. We propose that the vesicular membrane prevents the assembly of 65S-EC and keeps the pentamer antigenic CRP in the appropriate concentration and configuration for association with the nascent progeny RNA.

Antibodies, Monoclonal↗
PubMed1992

Structural and functional characterization of the poliovirus replication complex.

Two populations of membrane-bound replication complexes were isolated from poliovirus-infected HEp-2 cells by sucrose gradient centrifugation. The two fractions show similar ultrastructural features: the replication complex is enclosed in a rosettelike shell of virus-induced vesicles and contains a very tightly packed second membrane system (compact membranes). The vesicular fraction, which bands in 30% sucrose, contains replicative intermediate (RI) and 36S RNA. The fraction banding in 45% sucrose contains only minute amounts of RI and contains mainly 36S RNA, two-thirds of which is encapsidated. In vitro, the two fractions show similar RNA synthesizing capacities and produce 36S plus-strand RNA. Dissolving the membranes within and around synthetically active replication complexes with sodium deoxycholate abolishes the completion of 36S RNA but still allows elongation in the RI. Our findings suggest an architecture of the replication complex that has the nascent plus strands on the RI enclosed in the compact membranes and the replication forks wrapped additionally in protein. Plus-strand RNA can be localized by in situ hybridization with a biotinylated riboprobe between the replication complex and the rosette of the virus-induced vesicles. It was found that the progeny RNA strands are set free soon after completion from the replication complex at the sites where the compact membranes within the replication complex are in close contact with the surrounding virus-induced vesicles.

Cells, Cultured↗
PubMed1991

Functional heterogeneity of CD4-positive T-cell subsets: the correlation between effector functions and lymphokine secretion is limited.

Several effector functions and the lymphokine secretion pattern of 30 antigen-specific CD4+ T-cell clones have been investigated. The clones were generated directly by limiting dilution cloning of nylon wool-purified T-cells obtained from KLH immunized BALB/c mice and avoiding an initial bulk culture phase. Using this approach the CD4+ T-cell clones were grouped into helper and nonhelper subsets. Among the helper subset, clones which helped B-cells for specific antibody production by either cognate or noncognate recognition were identified. Some but not all of these helper clones fitted into the Th1 and Th2 scheme, if the lymphokine secretion pattern was evaluated. Among the nonhelper subset CD4+ clones which killed activated APC in a MHC class II-restricted and antigen-specific manner were identified. In addition, one clone which suppressed B-cell antibody production mediated by helper clones was found. However, neither the suppression of antibody responses nor the inability of the nonhelper clones to help B-cells is due to the killing of B-cells. Various attempts were made to convert nonhelper into helper clones and helper into killer clones, without success. Thus, the functional properties of these clones are stable traits and not convertible by varying the experimental conditions.

Animals↗
PubMed1990

CD4+ T cell-mediated killing of MHC class II-positive antigen-presenting cells. I. Characterization of target cell recognition by in vivo or in vitro activated CD4+ killer T cells.

Ag-specific as well as Ia-restricted killing of certain APC by CD4+ T cells was investigated. The CD4-mediated killing is not only a characteristic of in vitro long term cultured T cell lines or clones, but is also manifest after in vivo priming. Thus, CD4+ killer T cells are generated in vivo as well. CD4+ killer T cells are detected in the Th1, but not in the Th2 subset, and they do not appear to lyse Ia+ APC or bystander cells by a pathway mediated by secreted T cell factors. The latter observation is demonstrated by cold target inhibition experiments as well as by the failure of puromycin to inhibit killing, if applied in doses which completely block lymphokine secretion. Ia+ APC differ in their susceptibility to lysis. Transformed APC are usually better lysed than nontransformed APC. Unstimulated B cells are not killed, while LPS-stimulated B cell blasts are killed. The results of cold target inhibition and bystander killing experiments suggest that CD4+ killer T cells are activated by the common pathway, i.e., by Ag presented in the context of Ia, but killing requires the recognition of additional determinant(s) on APC. It is proposed that these killing-inducing determinants are continuously expressed on most transformed Ia+ cells and on nontransformed but stimulated APC.

Animals↗
PubMed1990

In situ hybridization for light and electron microscopy: a comparison of methods for the localization of viral RNA using biotinylated DNA and RNA probes.

We report procedures for in situ hybridization at the light and electron microscopic level for localization of viral RNA in poliovirus-infected, Lowicryl-embedded cells. We compare specificity and signal intensity of biotinylated, double-stranded DNA and single-stranded, strand-specific RNA probes, both corresponding to the same region of the poliovirus genome. The hybrids were detected with antibiotin antibodies or streptavidin with colloidal gold as a marker. Hybridization with the RNA probe was more sensitive and gave lower background than with DNA. Detection with immunogold proved to be by far more sensitive than with streptavidin. The hybridization and detection protocols for the DNA and the RNA probes could be applied without modification to light microscopic semi-thick sections as well as to electron microscopic ultrathin sections.

Biotin↗
PubMed1990

Structural organization of poliovirus RNA replication is mediated by viral proteins of the P2 genomic region.

Transcriptionally active replication complexes bound to smooth membrane vesicles were isolated from poliovirus-infected cells. In electron microscopic, negatively stained preparations, the replication complex appeared as an irregularly shaped, oblong structure attached to several virus-induced vesicles of a rosettelike arrangement. Electron microscopic immunocytochemistry of such preparations demonstrated that the poliovirus replication complex contains the proteins coded by the P2 genomic region (P2 proteins) in a membrane-associated form. In addition, the P2 proteins are also associated with viral RNA, and they can be cross-linked to viral RNA by UV irradiation. Guanidine hydrochloride prevented the P2 proteins from becoming membrane bound but did not change their association with viral RNA. The findings allow the conclusion that the protein 2C or 2C-containing precursor(s) is responsible for the attachment of the viral RNA to the vesicular membrane and for the spatial organization of the replication complex necessary for its proper functioning in viral transcription. A model for the structure of the viral replication complex and for the function of the 2C-containing P2 protein(s) and the vesicular membranes is proposed.

Antibodies, Monoclonal↗
PubMed1983

Functional characterization of T lymphocytes grown in semisolid agar.

T lymphocyte colony forming cells (TL-CFC) grown in agar in the presence of PHA were assayed for their capacity to induce or suppress polyclonal PWM dependent B lymphocyte differentiation into plasma cells. This was measured by identifying cells containing intracytoplasmatic immunoglobulins by direct immunofluorescence. To validate the helper and suppressor system used in this paper, the inductive capacity of unfractionated T lymphocytes and their subpopulations bearing Fc-receptors for IgM (TM) and for IgG (TG) was measured. The unfractionated T cells and the TM fraction showed helper activity, whereas the TG cells expressed suppressor activity. The TL-CFC grown in agar in the presence of PHA manifested helper activity at low cell concentration. However, increasing the TL-CFC concentration finally caused suppression of B cell differentiation. The suppressor effect could be abolished by prior irradiation of the TL-CFC before seeding them in agar. These results indicate that T cells grown in agar have the functional capacity of T helper and T suppressor cells to induce and suppress polyclonal PWM dependent B lymphocyte differentiation into plasma cells.

B-Lymphocytes↗