Structure-function studies of the C3a-receptor: C-terminal serine and threonine residues which influence receptor internalization and signaling

The anaphylatoxic peptide C3a is a pro-inflammatory mediator generated during complement activation, whose specific G protein coupled receptor is expressed on granulocytes, monocytes, mast cells, activated lymphocytes, and in the nervous tissue. We have generated RBL-2H3 cell clones stably expressing mutants of the human C3a-receptor (C3aR) with combined alanine (Ala) substitutions of ten C-terminal serine (Ser) or threonine (Thr) residues, which may represent putative phosphorylation sites to characterize their role in ligand-induced C3aR internalization and signaling. Ser475/479 and Thr480/481 as well as Ser449 seemed not to be involved in ligand-induced receptor internalization. Either directly or by a conformational change they even "inhibit" C3aR internalization. In contrast, mutants with Ala substitutions at Ser465/470 and Thr463/466 were poorly internalized, and Thr463 seemed to be the most important C-terminal Thr or Ser residue directly effecting receptor internalization. However, it is likely that other C3aR regions additionally participate in this negative feed-back mechanism since even mutants with multiple Ala substitutions still internalized to a limited degree. Interestingly, in a mutant with a single exchange of Ser449 to Ala, the signal transduction assessed by a Ca(2+) assay and [(35)S]GTP gamma S-binding on HEK cells transiently co-transfected with G-alpha 16 or G-alpha O, respectively, was severely impaired, indicating that this residue of C3aR is involved in G protein coupling.     

Circulating complement proteins in patients with sepsis or systemic inflammatory response syndrome.

The systemic inflammatory response of the body to invading microorganisms, termed sepsis, leads to profound activation of the complement system. Pathophysiological concepts suggest that complement activation occurs very early in this syndrome. Thus, we discuss whether the determination of concentrations of the complement components C3a, C5a, and C3 in plasma as well as of the C3a/C3 ratio might be helpful to diagnose sepsis early. For this purpose, 33 patients from an intensive care unit were monitored for 10 days. In comparison with healthy donors, C3a levels and the C3a/C3 ratio of intensive-care-unit patients were significantly elevated (P < 0.0001) on admission. In contrast, C3 levels were significantly reduced (P < 0.0001) but increased during the study. C5a levels in the plasma of healthy donors and patients were identical. Twenty-two of 33 patients fulfilled microbiological and clinical criteria of sepsis. Eleven patients had signs of systemic inflammatory response syndrome but no microbiological evidence of sepsis. The groups could be differentiated from each other by their C3a levels or their C3a/C3 ratios during the first 24 h after the clinical onset of sepsis (P < 0.05). Septic patients in shock had higher C3a levels than normotensive septic patients, although the differences were not significant. Nonsurvivors had significantly higher C3a levels on admission than survivors (P = 0.0185). No differences were found between septic patients who developed adult respiratory distress syndrome and those who did not. Thus, determination of C3a concentrations in plasma may prove useful (i) to diagnose sepsis early, (ii) to differentiate between patients with sepsis and those with systemic inflammatory response syndrome, and (iii) to assess prognosis.     

Mitogenicity of Entamoeba histolytica extracts for murine lymphocytes.

Aqueous extracts or aqueous extracts of delipidated Entamoeba histolytica (E.h.e.) contain a mitogenic principle for murine lymphocytes. As detected by [3H]-thymidine incorporation and blast transformation, E.h.e. acted predominantly on T cells of splenic origin, but not on thymocytes or bone marrow cells. Furthermore, E.h.e. induced proliferation of a subset of non-T-cells which is present in the spleen of athymic nude mice, adhered to nylon wool, but could not be activated to produce antibody. It seems possible that polyclonal activation of lymphocytes by E. histolytica might play a role in the disturbance of the immune system as manifested in the impaired cell mediated immune response of E. histolytica infected hosts.     

Guinea pig C3 specific rabbit single chain Fv antibodies from bone marrow, spleen and blood derived phage libraries

We constructed combinatorial immunoglobulin libraries from the whole rabbit antibody repertoire of bone marrow, spleen and peripheral blood of a rabbit immunized with guinea pig complement protein C3. By means of the phage display technology we selected guinea pig C3 specific single chain Fv (scFv) antibodies from each of the libraries. None of the scFv antibodies cross reacted with guinea pig C3a, human C3 or rat C3. The frequency of bone marrow derived C3 positive clones was much higher as compared to blood or spleen derived clones. Additionally bone marrow and spleen derived clones show higher diversity than clones, obtained from blood, as determined by fingerprint analysis with the restriction enzyme AluI. Dissociation rate constants for all scFvs were similar, indicating that the source of the scFvs had no influence on affinities. The antibody fragments were used to analyze complement activation during xenotransplantation. Several blood or bone marrow derived scFvs bound to C3 located on rat liver endothelium after hyperacute rejection of a heterotopically transplanted rat liver into guinea pig. These data demonstrate that monoclonal rabbit scFvs can be easily generated from recombinant phage display libraries, constructed from spleen, blood or bone marrow. The selected guinea pig C3 specific scFvs appear to be useful to detect complement activation during xenotransplantation in guinea pigs.     

CRIGOS: development of a compact robot for image-guided orthopedic surgery

In this paper, we present a medical robot system dedicated to support the surgeon during challenging tasks within orthopedic interventions. The main goal of this work is to develop a system as technically simple as the surgical requirements allow to keep its cost and complexity to a minimum. Therefore, we primarily focus on calibrated X-ray imaging for image acquisition, an easy registration procedure and robotic execution using a positioning device with simple parallel kinematics. Examples of different orthopedic interventions using the compact robot system for image-guided orthopedic surgery (CRIGOS) are presented, as well as various modes of execution of the device.     

Short-term prognosis in critically ill patients with liver cirrhosis: an evaluation of a new scoring system

OBJECTIVE: The mortality of patients with liver cirrhosis admitted to an intensive care unit (ICU) has been found to be high. This study was performed to assess the physiological and laboratory parameters which are able to identify on ICU admission the cirrhotic patients who are most likely to die. DESIGN: Prospective clinical trial. METHODS: Two groups of patients were analysed. Group A consisted of 196 consecutive cirrhotic patients admitted to our medical ICU for various reasons. For the detection of independent outcome predictors, we used a multiple logistic regression model. Based on these variables, the 'intensive care cirrhosis outcome (ICCO) score' was calculated. The ability to discriminate between survivors and non-survivors was determined by receiver operating characteristic curves, and the area under the curve was calculated. Group B consisted of 70 consecutive cirrhotic patients for prospective validation of the ICCO score. RESULTS: Applying multiple logistic regression analysis, bilirubin, cholesterol, creatinine clearance and lactate were found to be independently associated with the hospital mortality. The ICCO score was 0.3707 + (0.0773 x bilirubin (mg/dl)) - (0.00849 x cholesterol (mg/dl)) -(0.0155 x creatinine clearance (ml/min)) + (0.1351 x lactate (mmol/l)), giving an area under a receiver operating characteristic curve of 0.9. Increasing score values were associated with an increase in mortality. All patients with an ICCO score > +2.6 died. CONCLUSIONS: Application of the ICCO score is rapid and available at the patient's bedside, and its application is simple and reproducible. In cirrhotic patients, the ICCO score has a high ability to discriminate between survivors and non-survivors. The ICCO score may facilitate estimation on ICU admission of the prognosis of critically ill cirrhotic patients.     

Modified Lapidus arthrodesis with plantar plate and compression screw for treatment of hallux valgus with hypermobility of the first ray: A preliminary report

BackgroundTMT-1 arthrodesis is an established method in hallux valgus surgery, but it is technically demanding and typically calls for a period of postoperative immobilization.MethodsIn this cohort study, initial experience with a plantar plate is described. 58 patients (59 arthrodesis) were included.ResultsThe mean duration of protected full weight bearing was 7 weeks. 94.12% patients were satisfied with the results, bony union was achieved in 98.31%. The Foot Function Index improved by 33 to a mean of 8 (p < .001). The postoperative Mayo Clinic Forefoot Score was excellent in 47.04 and good in 47.04%. The mean hallux valgus angle improved by 24.4–13.2° (p < .001). The mean first intermetatarsal angle improved by 11.2–5.2° (p < .001).ConclusionInitial experience with this form of fixation appears to provide suitable stability, allow early-protected weight bearing, with an acceptable level of complications.