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Biomedical subjects

S Radtke

Publications and source records attributed to S Radtke.

8 recordsLinked to original sources
PubMed2005

The effect of suture materials and techniques on the outcome of repair of the rotator cuff: a prospective, randomised study.

In a prospective, randomised study on the repair of tears of the rotator cuff we compared the clinical results of two suture techniques for which different suture materials were used. We prospectively randomised 100 patients with tears of the rotator cuff into two groups. Group 1 had transosseous repair with No. 3 Ethibond using modified Mason-Allen sutures and group 2 had transosseous repair with 1.0 mm polydioxanone cord using modified Kessler sutures. After 24 to 30 months the patients were evaluated clinically using the Constant score and by ultrasonography. Of the 100 patients, 92 completed the study. No significant statistical difference was seen between the two groups: Constant score, 91% vs 92%; rate of further tear, 18% vs 22%; and revision, 4% vs 4%. In cases of further tear the outcome in group 2 did not differ from that for the intact repairs (91% vs 91%), but in group 1 it was significantly worse (94% vs 77%, p = 0.005). Overall, seven patients had complications which required revision surgery, in four for pain (two in each group) and in three for infection (two in group 1 and one in group 2).

Adult↗
PubMed2001

[Coronary risk profile in women with angiographically normal coronary arteries or initial coronary arteriosclerosis].

The pathophysiology and prognosis of coronary heart disease in women are the subject of intensive epidemiological and clinical investigations due to sex specific considerations. We have estimated the prevalence of modifiable coronary risk factors in 36 consecutive women (mean age 59.7 years) with suspected coronary heart disease in whom coronary angiography was performed due to unclear chest pain. Seventeen women revealed angiographically normal coronary arteries (gr. I) and 19 women showed coronary vessels with initial arteriosclerosis (luminal diameter reduction < 35%) (gr. II). Mean age was 59.1 years in gr. I and 60.3 years in gr. II (p = ns). No woman received lipid lowering drugs within the last 6 months. A hormone replacement therapy was not performed in any case. Women in gr. I showed significantly higher total and LDL cholesterol levels (271.6 +/- 34.3 vs 243.5 +/- 44.8 mg/dl; p < 0.005 and 190.5 +/- 36.8 vs 149.7 +/- 45.1 mg/dl; p < 0.025, respectively) and significantly lower HDL cholesterol values (57.8 +/- 16.5 vs 72.8 +/- 19.1 mg/dl; p < 0.0125) compared to women in gr. II. The total/HDL cholesterol ratio was 3.6 +/- 1.2 in gr. I and 5.1 +/- 1.7 in gr. II (p < 0.005). The positive predictive value for the existence of initial coronary atherosclerosis and a total cholesterol/HDL ratio > 4 was 76.5%. The negative predictive value and a ratio < 4 was 81.3%. Women in gr. I revealed 1.2 +/- 0.9 and in gr. II 1.6 +/- 0.8 risk factors (smoking, hypertension, body mass index > 30 kg/m2, diabetes mellitus, hyperlipidemia) (p < 0.10). The 10-year risk for the occurrence of a coronary event was 9.1 +/- 3.7% in gr. I and 14.2 +/- 5.8% in gr. II (p < 0.005). The positive predictive value for the existence of initial coronary atherosclerosis and a 10-year risk > 10% was 90%. The negative predictive value and a 10-year risk < 10% was 64.0%. Our investigation indicates that women with a mean age of 60 years, unclear chest pain and without exercise induced ischemia are highly suspected to have initial coronary arteriosclerosis, when a distinct risk factor profile and a 10-year cardiac event risk > 10% are present. For this high risk group of women, intensive secondary prevention measures are necessary.

Aged↗
PubMed2000

Non-redundant signal transduction of interleukin-6-type cytokines. The adapter protein Shc is specifically recruited to rhe oncostatin M receptor.

The common use of the cytokine receptor gp130 has served as an explanation for the extremely redundant biological activities exerted by interleukin (IL)-6-type cytokines. Indeed, hardly any differences in signal transduction initiated by these cytokines are known. In the present study, we demonstrate that oncostatin M (OSM), but not IL-6 or leukemia inhibitory factor, induces tyrosine phosphorylation of the Shc isoforms p52 and p66 and their association with Grb2. Concomitantly, OSM turns out to be a stronger activator of ERK1/2 MAPKs. Shc is recruited to the OSM receptor (OSMR), but not to gp130. Binding involves Tyr(861) of the OSMR, located within a consensus binding sequence for the Shc PTB domain. Moreover, Tyr(861) is essential for activation of ERK1/2 and for full activation of the alpha(2)-macroglobulin promoter, but not for an exclusively STAT-responsive promoter. This study therefore provides evidence for qualitative differential signaling mechanisms exerted by IL-6-type cytokines.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Signal transduction of IL-6, leukemia-inhibitory factor, and oncostatin M: structural receptor requirements for signal attenuation.

Stimulation of the IL-6R complex leads to Src homology domain containing tyrosine phosphatase 2 (SHP2) recruitment to the receptor subunit gp130 and its subsequent tyrosine phosphorylation. SHP2 is a two-SH2 domain-containing protein tyrosine phosphatase that is activated by many cytokines and growth factors. SHP2 counteracts the activation of transcription factors of the STAT family and the induction of IL-6-responsive genes. Tyrosine 759 of gp130, the signal transducing subunit of the IL-6R complex, is essential for the phosphorylation of SHP2. Mutation of tyrosine 759 to phenylalanine leads to an enhanced inducibility of IL-6-dependent genes. Here we demonstrate that no further tyrosines in the cytoplasmic part of gp130 are required for the phosphorylation of SHP2. We also tested whether the tyrosine 759 motifs in both subunits of the gp130 dimer are required for SHP2 association and tyrosine phosphorylation. Interestingly, one SHP2-recruiting phosphotyrosine motif in a single chain of the gp130 dimer is sufficient to mediate SHP2 association to the gp130 receptor subunit and its tyrosine phosphorylation as well as to attenuate IL-6-dependent gene induction. Furthermore, we show that repression of gene induction via Y759 does not require the presence of the SHP2 and STAT recruitment sites within the same receptor subunit, but within the same receptor complex. The Y759 motif in gp130 also attenuates gene induction mediated by the oncostatin M and leukemia inhibitory factor receptor complexes, which both contain gp130 as the shared subunit.

Acute-Phase Proteins↗
PubMed2000

Differential inhibition of IL-6-type cytokine-induced STAT activation by PMA.

Prior activation of mitogen-activated protein kinases by phorbol 13-myristate 12-acetate (PMA) results in an inhibition of interleukin (IL)-6-induced activation of the Janus kinase/signal transducer and activator of transcription (STAT) signaling pathway which is most likely mediated by the induction of suppressor of cytokine signaling-3 and requires the specific SHP2 binding site Y759 of the IL-6 signal transducer gp130. In this study, we demonstrate that PMA inhibits STAT activation by IL-6 and the related cytokine leukemia inhibitory factor (LIF) but not by oncostatin M (OSM). Since the LIF receptor also contains an SHP2 recruitment site whereas the OSM receptor lacks such a module, we propose that two SHP2 binding modules within a homo- or heterodimeric receptor are necessary to mediate the PMA inhibitory effect.

Amino Acid Motifs↗
PubMed1999

Contributions of leukemia inhibitory factor receptor and oncostatin M receptor to signal transduction in heterodimeric complexes with glycoprotein 130.

Leukemia inhibitory factor (LIF), cardiotrophin-1, ciliary neurotrophic factor, and oncostatin M (OSM) lead to heterodimerization of LIF receptor (LIFR) or the OSM-specific receptor (OSMR) with glycoprotein (gp) 130, the common receptor subunit for IL-6-type cytokines. Thereby intracellular signaling via Janus kinases (Jaks) and STAT transcription factors is initiated. We investigated the contributions of LIFR and OSMR to signal transduction in the context of heterodimers with gp130. Chimeric receptors based on the extracellular parts of the IL-5R alpha- and beta-chains were generated, allowing the induced heterodimerization of two different cytoplasmic tails. Our studies demonstrate that upon heterodimerization with the gp130 cytoplasmic region, the cytoplasmic parts of both LIFR and OSMR were critical for activation of an acute phase protein promoter in HepG2 hepatoma cells. The membrane-proximal region of LIFR or OSMR was crucial for the ability of such receptor complexes to induce DNA binding of STAT1 and STAT3 in COS-7 cells. Membrane-distal regions of LIFR and OSMR contributed to STAT activation even in the absence of gp130 STAT recruitment sites. We further show that the Janus kinases Jak1 and Jak2 constitutively associated with receptor constructs containing the cytoplasmic part of LIFR, OSMR, or gp130, respectively. Homodimers of the LIFR or OSMR cytoplasmic regions did not elicit responses in COS-7 cells but did in HepG2 cells and in MCF-7 breast carcinoma cells. Thus, in spite of extensive functional similarities, differential signaling abilities of gp130, LIFR, and OSMR may become evident in a cell-type-specific manner.

Animals↗