Adrenomedullin reduces Staphylococcus aureus alpha-toxin-induced rat ileum microcirculatory damage

OBJECTIVE

Increased microvascular permeability and perfusion mismatch are hallmarks of sepsis or septic shock. The intestinal mucosa is very sensitive to tissue hypoxia. Intestinal mucosa dysfunction may allow translocation of bacteria and their products, thereby perpetuating sepsis and inflammation. Staphylococcus aureus alpha-toxin is a major pathogenicity determinant of this bacterium, provoking cardiovascular collapse. Current evidence suggests that the endogenous peptide adrenomedullin stabilizes circulatory homeostasis in systemic inflammatory response. Using alpha-toxin as a well-defined strong initiator of an inflammatory reaction, we tested the hypothesis that exogenously applied adrenomedullin stabilizes gut microcirculation.

DESIGN

Prospective, experimental study.

SETTING

Research laboratory at a university hospital.

SUBJECTS

Isolated, perfused ileum from male Sprague-Dawley rats and human umbilical vein endothelial cells.

INTERVENTIONS

Administration of S. aureus alpha-toxin before or after infusion of adrenomedullin.

MEASUREMENTS AND MAIN RESULTS

Injection of a bolus of 1 microg of alpha-toxin in the superior mesenteric artery in a constant-flow, blood-perfused preparation of rat ileum increased perfusion pressure and relative hemoglobin concentration and decreased mucosal hemoglobin oxygen saturation. Continuous infusion of adrenomedullin (0.1 micromol/L) significantly reduced these alpha-toxin-related effects. Severe microvascular hyperpermeability observed in alpha-toxin-exposed ileum was abolished by adrenomedullin pretreatment. In addition, adrenomedullin blocked alpha-toxin-induced endothelial myosin light chain phosphorylation, endothelial cell contraction, and subsequent loss of endothelial barrier function in vitro. Treatment of alpha-toxin (infusion of 0.05 microg/mL)-exposed ileum with adrenomedullin (0.1 micromol/L) started 10 mins after onset of toxin application also significantly reduced superior mesenteric artery pressure and permeability increase.

CONCLUSIONS

In summary, these data suggest that exogenous adrenomedullin protects ileum by reducing alpha-toxin-induced microcirculatory disturbances and by stabilizing endothelial barrier function.

Porphyromonas gingivalis strain-dependent activation of human endothelial cells

Porphyromonas gingivalis is an important bacterium involved in periodontal diseases. Colonization by periodontopathogens has been associated with severe local inflammatory reactions in the connective tissue. In this study we characterized P. gingivalis-mediated infection and activation of human umbilical vein endothelial cells by using two strains of different virulence capacities, strains ATCC 53977 and DSMZ 20709. Both strains were able to adhere to and infect endothelial cells with an infection rate of 0.48% for ATCC 53977 and 0.007% for DSMZ 20709. The triggering of two signal transduction pathways in P. gingivalis-infected endothelial cells was demonstrated for both strains, with a rapid increase of p38 mitogen-activated protein kinase phosphorylation and a more delayed degradation of IkappaBalpha, followed by nuclear translocation of NF-kappaB. In addition, both strains induced enhanced expression of endothelial adhesion molecules E-selectin and intracellular adhesion molecule 1 (ICAM-1). Target cell activation was independent of bacterial fimbriae expression since the fimA knockout strain A7436 DeltafimA induced the same level of ICAM-1 as the corresponding wild type (A7436-WT). Thus, two P. gingivalis strains, ATCC 53799 and DSMZ 20709, infect endothelial cells and trigger signaling cascades leading to endothelial activation, which in turn may result in or promote severe local and systemic inflammation.

[Care of maxillary anterior gaps with ITI-Bonefit implants]

As for the Implantation in the upper frontal jaw region ITI-Bonefit-Implants show konceptional advantages to other systems. Surgical and prosthodontic techniques are demonstrated. In cases of extreme transversal atrophy segmental bone-splitting mostly makes implantation possible. First results from the dental clinic of Göttingen show a primary success rate of 100% in osteointegration and sufficient prosthodondic reconstruction.

[Current limitations of radial keratotomy]

The so-called R.K. classic technique gives good results for myopias under 5 diopters. We have performed different modifications of the technique for the 8 incisions--optical zone 3 mm R.K. 8 incisions--O.Z. 3 mm. Downhill incision direction or "American technique" incisions (from the O.Z. towards the limbus). 8 incisions--O.Z. 3 mm + a deepening of 20 microns from a 6 mm O.Z. Repeat operations (Stan Franks Backcutting technique or addition of incisions). 8 incisions--O.Z. 3 mm. Uphill incision direction or "Russian technique" (from the limbus towards the optical zone). This study was carried out with 134 R.K. and shows that we get best results for myopias between 5 to 7 diopters, with the last technique (Uphill incision direction).

Severe "suction injury" due to implosion of an underwater camera casing: mechanism of injury

The dynamics of a "suction injury" of soft tissues in a deep-sea diver caused by the implosion of a home-made camera casing at a depth of 40 m have been investigated. An unprotected rubber ring holding the window on the outside of the camera casing was apparently not sufficiently rigid to prevent the outward movement of the glass at the periphery and shattering inwards at the center as a result of pressure of 500 kg at a depth of 40 m.

Detachable balloon catheter. Its application in experimental arteriovenous fistulae

Recent Russian reports have described the use of balloon occlusion in both the diagnosis and treatment of various pathological processes affecting intracranial vessels. This intraluminal approach has demonstrated successful results in vascular problems such as carotid-cavernous fistulae, arteriovenous malformations, and large inoperable aneurysms. Despite widespread interest in the neurosurgical community, the application of a similar technique in the Western hemisphere has been hindered by lack of an adequate, functional, inflatable apparatus. The authors describe their experience with the prototype of a safe, reliable, detachable balloon. Because of a unique development, the apparatus may be filled with liquid and detached from its parent catheter without subsequent leakage. In order to satisfy variable requirements, balloons are available in several sizes ranging from 0.5 to 4.0 mm in diameter. When fully inflated these devices will hold from 1 to 3 cc of fluid. The authors' study involved 18 dogs with artificially created carotid-jugular fistulae that were visualized by angiography. Under fluoroscopic control, detachment of inflated balloons on the venous side of the defect not only successfully occluded the fistulae but also preserved the arterial vasculature. X-ray films taken several weeks later failed to show any change either in size or position of the inflated devices.