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Biomedical subjects

J Rieger

Publications and source records attributed to J Rieger.

At least 19 recordsLinked to original sources
PubMed2006

Controlled synthesis and interface properties of new amphiphilic PCL-g-PEO copolymers.

Novel biodegradable and biocompatible poly(epsilon-caprolactone)-graft-poly(ethylene oxide), PCL-g-PEO, copolymers consisting of biocompatible blocks have been synthesized by ring-opening copolymerization of epsilon-caprolactone (epsilon CL) and a poly(ethylene oxide) (PEO) macromonomer, i.e., PEO end-capped by an epsilon-caprolactone unit (gamma PEO.CL). The control is effective on the composition and length of both the hydrophobic polyester backbone and the hydrophilic PEO grafts. The reactivity ratios have been determined by monitoring the copolymer composition in relation to the comonomer conversion. The PCL-g-PEO copolymers have a tapered (gradient) rather than a random structure consistent with r(epsilon)CL = 3.95 and r(gamma)PEO.CL = 0.05. The amphiphilic graft copolymers display surfactant properties similar to those of PEO-b-PCL diblock copolymers of comparable composition and solubility, as supported by CHCl3/water interfacial tension measured by the pendant drop method.

Hydrophobic and Hydrophilic Interactions↗
PubMed2006

[Chronic critical ischemia of the lower leg: pretherapeutic imaging and methods for revascularization].

Each year 1-2% of patients with peripheral arterial occlusive disease (pAOD) develop critical limb ischemia (CLI), characterized by rest pain and peripheral ulcer or gangrene. This aggravation of the disease is accompanied by an increase of the 1-year mortality rate up to 25% and a similarly increased frequency of major amputation. We can choose between conservative, endovascular, and surgical procedures for an adequate therapy of the underlying vascular stenoses or occlusions. Yet, clear therapeutic recommendations only exist for suprapopliteal lesions. However, in a number of cases, especially in diabetics, target lesions have an infrapopliteal location. Since endovascular procedures have undergone significant improvement in the last few years, the following review discusses methods for infrapopliteal revascularization taking into consideration the newest publications on this topic.

Angioplasty↗
PubMed2006

[Stenting of the SFA--indications, techniques, results].

Aggressive risk factor modification, change of eating habits, exercise programs, and forceful antiplatelet therapy are the most important tools for the treatment of PAOD in symptomatic patients suffering from intermittent claudication. There are however no guidelines for revascularization at this stage. Endovascular treatment has been increasingly utilized over the last decade and increasingly displaced vascular surgery. Amongst numerous endovascular techniques beside PTA, stents meanwhile play the most important role due to constant technical progress. Results regarding the rate of restenosis or patency rates still remain worse compared to other vascular beds. This paper gives a review over recent results, currently available stent techniques, and possible indications for the endovascular therapy of an artery, which has turned out to be the biggest ordeal for material and construction of stents.

Blood Vessel Prosthesis↗
PubMed2006

Stenting of the superficial femoral artery after suboptimal balloon angioplasty: one-year results.

AIM: The aim of this study was to analyze the intermediate results of selective stenting of superficial femoral artery (SFA) lesions after a suboptimal balloon angioplasty result. METHODS: We analyzed 70 consecutive patients with claudication or critical limb ischemia due to peripheral arterial occlusive disease who underwent stent implantation of the SFA after unsuccessful balloon-angioplasty. All patients were followed-up immediately after the procedure and 3, 6 and 12 months thereafter. Restenosis was defined as an increase of peak systolic velocity-index >2 as determined by duplex sonography. RESULTS: Primary patency rates at 3, 6 and 12 months were 83.4%, 66.2% and 59%, respectively. Successful reinterventions were performed for 17 reobstructions, resulting in a secondary patency rate at 3, 6 and 12 months of 91%, 89.3%, and 83.8%, respectively. At 12 months 68.6% of the patients were asymptomatic, 21.6% complained of mild (Fontaine class II a), 5.9% of severe (Fontaine class II b) claudication and 2.9% were in critical limb ischemia. CONCLUSIONS: Our data indicate that selective stenting of the SFA after suboptimal balloon angioplasty results in intermediate patency rates similar to that reported for primarily successful PTA, thereby supporting the widely accepted policy of selective stenting as a rescue procedure after unsuccessful balloon angioplasty.

Aged↗
PubMed2005

BCL-xL: time-dependent dissociation between modulation of apoptosis and invasiveness in human malignant glioma cells.

Conditionally BCL-xL-overexpressing LNT-229 Tet-On glioma cell clones were generated to investigate whether the 'antiapoptosis phenotype' and the 'motility phenotype' mediated by BCL-2 family proteins in glioma cells could be separated. BCL-xL induction led to an immediate and concentration-dependent protection of LNT-229 cells from apoptosis. BCL-xL induction for up to 3 days did not result in altered invasiveness. In contrast, long-term BCL-xL induction for 21 days resulted in increased transforming growth factor-beta2 expression, and in metalloproteinase-2 and -14 dependent, but integrin independent, increased invasiveness. Withdrawal of doxycycline (Dox) abolished the protection from apoptosis whereas the 'invasion phenotype' remained stable. Dox stimulation of BCL-xL-inducible LNT-229 cells conferred infiltrative growth to BCL-xL-positive glioma cells in vivo and reduced the survival of tumor-bearing mice. These data allow to dissect a direct antiapoptotic action of BCL-xL from an indirect effect, presumably mediated by altered gene expression, which modifies tumor cell invasiveness in vitro and in vivo.

Animals↗
PubMed2005

Adult medulloblastoma: prognostic factors and response to therapy at diagnosis and at relapse.

Adult medulloblastoma is a rare tumor with few retrospective studies published so far. The role of adjuvant chemotherapy or chemotherapy at relapse is unclear. This study reports therapy and outcome in all adult (>or=16 years old) medulloblastoma (n=34) and supratentorial primitive neuroectodermal tumor (PNET) patients (n=2) treated in 2 neuro-oncological centers between 1976 and 2002. The median age was 24.5 years (range 16-76). After resection, 16 patients were treated with craniospinal radiotherapy alone, 20 patients also received adjuvant chemotherapy (8 vincristine, CCNU, cisplatin; 7 methotrexate alone or methotrexate/vincristine-based polychemotherapy; 5 other protocols). Median survival in the whole cohort was 126 months (2+ - 200+months). Five-year and 10-year survival rates were 79 % and 56%. Adjuvant chemotherapy was associated with a non-significant trend to prolonged survival (relative risk (RR) 1.89; p=0.068). The median progression-free survival (PFS) after primary therapy was 83 months. At relapse, 10 of 12 evaluable patients achieved a complete response upon second-line therapy. The median survival times from first (n=17) and second relapse (n=9) were 21 months (0-67+ months; 5/17 without second relapse) and 20 months (1-29 months). Cox regression analysis revealed the infiltration of the floor of the 4(th) ventricle at diagnosis as the only therapy-independent prognostic factor (RR 0.48; p=0.03). In conclusion, adjuvant chemotherapy may prolong survival in adult medulloblastoma patients. Moreover, second-line therapy may be beneficial for these patients. As in pediatric medulloblastoma patients, primary infiltration of the floor of the 4(th) ventricle indicates a poor prognosis.

Adolescent↗
PubMed2005

[Possibilities for workflow optimization in radiology departments beyond RIS and PACS].

Technological progress and the rising cost pressure on the healthcare system have led to a drastic change in the work environment of radiologists today. The pervasive demand for workflow optimization and increased efficiency of its activities raises the question of whether by employment of electronic systems, such as RIS and PACS, the potentials of digital technology are sufficiently used to fulfil this demand. This report describes the tasks and structures in radiology departments, which so far are only insufficiently supported by commercially available electronic systems but are nevertheless substantial. We developed and employed a web-based, integrated workplace system, which simplifies many daily tasks of departmental organization and administration apart from well-established tasks of documentation. Furthermore, we analyzed the effects exerted on departmental workflow by employment of this system for 3 years.

Database Management Systems↗
PubMed2005

Refractory Takayasu's arteritis successfully treated with the human, monoclonal anti-tumor necrosis factor antibody adalimumab.

Treatment of Takayasu's arteritis remains a demanding challenge to clinicians. In many patients the course of the disease is characterized by frequent relapses and disease progression under conventional treatment with glucocorticoids and cytotoxic drugs. We present the case of a young woman with severe cerebrovascular and aortic involvement, who experienced disease progression in spite of more than 2 years of treatment with high doses of prednisone, methotrexate and cyclophosphamide. In this patient, treatment with the human, monoclonal anti-tumor necrosis factor-alfa (TNFalfa)-antibody adalimumab achieved clinical remission and allowed tapering of prednisone within a few months. The present case, as well as previous reports on the use of infliximab in giant cell and Takayasu's arteries, suggests that TNFa-blockade may be a new, promising treatment for glucocorticoid-refractory large-vessel vasculitis.

Adalimumab↗
PubMed2004

IT services in a completely digitized radiological department: value and benefit of an in-house departmental IT group.

To analyze the benefit of a departmental IT group in comparison to support by hospital IT groups or system manufacturers in a completely digitized radiological department. The departmental IT group comprises a fulltime IT specialist, two student assistants and four clinical employees participating 1 day/week. For 18 months IT problems were quantified and specified according to urgency, responsibility and affected system by use of an intranet-based reporting system. For each IT service provider the performance and duration of problem solution was evaluated. In 18 months 3,234 IT problems emerged. 88.7% were solved by the departmental IT group. In 474 cases (14.7%) a solution within 2 h was required. The departmental IT group solved 35.8% within 30 min, system manufacturers needed 18 h 38 min in mean. The departmental IT group solved 90.2% of the problems within a time limit. System manufacturers met the limit in 60.1% with a mean duration of 7 days 21 h. In 6.7% of the cases, support by system manufacturers was indispensable. A considerable proportion of IT problems in completely digitized radiological departments can be solved by a departmental IT group, providing a fast and cost-efficient first-level IT support with effective prevention of major breaks in the workflow. In a small number of cases support by system manufacturers remains necessary.

Computer Communication Networks↗
PubMed2004

The mobility of the amorphous phase in polyethylene as a determining factor for slow crack growth.

Polyethylene (PE) pipes generally exhibit a limited lifetime, which is considerably shorter than their chemical degradation period. Slow crack growth failure occurs when pipes are used in long-distance water or gas distribution though being exposed to a pressure lower than the corresponding yield stress. This slow crack growth failure is characterized by localized craze growth and craze fibril rupture. In the literature, the lifetime of PE pipes is often considered as being determined by the density of tie chains connecting adjacent crystalline lamellae. But this consideration cannot explain the excellent durability of the recent bimodal grade PE for pipe application. We show in this paper the importance of the craze fibril length as the determining factor for the pipe lifetime. The conclusions are drawn from stress analysis. It is found that longer craze fibrils sustain lower stress and are deformed to a lesser degree. The mobility of the amorphous phase is found to control the amount of material that can be "sucked" in by the craze fibrils and thus the length of the craze fibrils. The mobility of the amorphous phase can be monitored by dynamic mechanical analysis measurements. Excellent agreement between the mobility thus derived and lifetimes of PE materials as derived from FNCT (full notch creep test) is given, thus providing an effective means to estimate the lifetime of PE pipes by considering well-defined physical properties.

Journal Article↗
PubMed2004

Alkylphosphocholine-induced glioma cell death is BCL-X(L)-sensitive, caspase-independent and characterized by massive cytoplasmic vacuole formation.

Alkylphosphocholines (APC) are candidate anticancer agents. We here report that APC induce the formation of large vacuoles and typical features of apoptosis in human glioma cell lines, but not in immortalized astrocytes. APC promote caspase activation, poly(ADP-ribose)-polymerase (PARP) processing and cytochrome c release from mitochondria. Adenoviral X-linked inhibitor of apoptosis (XIAP) gene transfer, or exposure to the caspase inhibitor, benzyloxycarbonyl-Val-Ala-DL-Asp-fluoro-methylketone zVAD-fmk, blocks caspase-7 and PARP processing, but not cell death, whereas BCL-X(L) blocks not only caspase-7 and PARP processing but also cell death. APC induce changes in Delta Psi m in sensitive glioma cells, but not in resistant astrocytes. The changes in Delta Psi m are unaffected by crm-A (cowpox serpin-cytokine response modifier protein A), XIAP or zVAD-fmk, but blocked by BCL-X(L), and are thus a strong predictor of cell death in response to APC. Free radicals are induced, but not responsible for cell death. APC thus induce a characteristic morphological, BCL-X(L)-sensitive, apparently caspase-independent cell death involving mitochondrial alterations selectively in neoplastic astrocytic cells.

Antineoplastic Agents↗
PubMed2003

Depletion-induced phase separation in colloid-polymer mixtures.

Phase separation can be induced in a colloidal dispersion by adding non-adsorbing polymers. Depletion of polymer around the colloidal particles induces an effective attraction, leading to demixing at sufficient polymer concentration. This communication reviews theoretical and experimental work carried out on the polymer-mediated attraction between spherical colloids and the resulting phase separation of the polymer-colloid mixture. Theoretical studies have mainly focused on the limits where polymers are small or large as compared to the colloidal size. Recently, however, theories are being developed that cover a wider colloid-polymer size ratio range. In practical systems, size polydispersity and polyelectrolytes (instead of neutral polymers) and/or charges on the colloidal surfaces play a role in polymer-colloid mixtures. The limited amount of theoretical work performed on this is also discussed. Finally, an overview is given on experimental investigations with respect to phase behavior and results obtained with techniques enabling measurement of the depletion-induced interaction potential, the structure factor, the depletion layer thickness and the interfacial tension between the demixed phases of a colloid-polymer mixture.

Journal Article↗
PubMed2003

Early stages of particle formation in precipitation reactions-quinacridone and boehmite as generic examples.

For many products, such as nanoparticulate systems, particle formation by precipitation is an essential procedural step. To learn more about the processes involved in precipitation, we investigated particle formation during precipitation reactions by means of online and offline methods. As model systems we chose the catalyst boehmite and the organic pigment quinacridone. The reactants were mixed in a mixing device and led into a reaction tube. At the end of the tube, a free jet of the suspension was produced. By varying the length of the reaction tube the time between mixing the reactants and the moment of observation was varied. Thus a time resolution down to 10 ms from the beginning of the reaction was obtained. Small-angle X-ray scattering on the free jet yielded online information about the structural inhomogeneities within the reacting systems. Transmission electron microscopy patterns obtained from quenched samples, which were taken by shooting copper grids through the free jet into liquid nitrogen, provided complementary information about structural features. Immediately after mixture an emulsion-like structure develops indicating that classical nucleation theory does not apply in the present systems. This finding can be explained by assuming instantaneous reaction at the interfaces of the two reactants that meet in the mixing device. From this preliminary state primary particles form with a size in the nanometer range. The observations can be rationalized by considering the underlying hydrodynamics of turbulent mixing of the reactants.

Journal Article↗
PubMed2003

[Costs and benefits of an education program for patients with ankylosing spondylitis as part of an inpatient rehabilitation programs-study design and first results].

The economic evaluation of a patient education program "ankylosing spondylitis"-based on a randomised controlled prospective multi-center study design-compares program costs and savings in direct and indirect follow-up costs. The collection of health services and cost data was conducted by questioning staff (education programme costs) and patients (follow-up costs). The present study results are: program costs per patient range between 117 euro (10 participants per course) and 186 euro (6 participants per course). Savings in indirect costs (unfitness to work) amount to 2500 euro and thus overcompensate program costs. Currently patient data are verified by sickness fund data and direct follow-up costs and qualitiy of life data are analysed.

Cost Savings↗
PubMed2003

[CT-guided aortic balloon occlusion in traumatic abdominal and pelvic bleeding].

PURPOSE: To introduce a new interventional method for CT-guided aortic balloon occlusion in patients with life-threatening abdominal or pelvic bleeding. MATERIALS AND METHODS: Three male patients (age 18, 30, and 45 years) with multiple trauma underwent CT-guided balloon occlusion of the aorta after CT identified an active abdominal or pelvic bleeding site and the patients became unstable (systolic blood pressure, BP < 80 mm Hg) despite resuscitation continuous volume. Using a right femoral approach, a 9F sheath was immediately introduced and the positions of the guide wire and balloon catheter (20 x 40 mm) were intermittently checked with CT scans and CT fluoroscopy. In one case, a C-clamp was applied to the pelvic ring under CT guidance for emergency stabilization of an unstable pelvic fracture. RESULTS: CT-guided aortic balloon occlusion and the mounting of the pelvic C-clamp were technically successful. Intervention time was 4 to 6 minutes for aortic balloon occlusion. All patients became at least temporarily stable hemodynamically with the blood pressure rising above 100 mmHg. The infrarenal occlusion catheters were left in place up to 60 minutes. Suprarenal occlusion was not performed. Two patients died due to protracted shock and complex injuries (injury severity score (ISS: 50 - 64). CONCLUSION: CT-guided aortic occlusion provides fast and effective bleeding control immediately after completion of the diagnostic CT. The procedure can be combined with other specific emergency surgical or interventional procedures. Experience with more patients is necessary for further evaluation of this new technique.

Adolescent↗
PubMed2003

Intrapericardial instillation of mitoxantrone in palliative therapy of malignant pericardial effusion.

BACKGROUND: Pericardial effusions occurring with pericardial or myocardial metastases often cause serious complications, necessitating temporary or emergency relief by percutaneous pericardiocentesis. However, this often results in recurrences. For long-term therapy success, the intrapericardial instillation of anti-neoplastic agents is an alternative to surgical methods, which are stressful for the patient. Following our positive experiences with mitoxantrone in the treatment of malignant pleural effusions, we applied this substance for the therapy of malignant pericardial effusions. PATIENTS AND METHODS: 16 patients with cytologically verified malignant pericardial effusions (8 with bronchial carcinoma, 7 with carcinoma of the breast, 1 with adenocarcinoma of the stomach) received an intrapericardial instillation of mitoxantrone 1-3 x10-20 mg. Responses were evaluated by echocardiography 30 days after completion of therapy. RESULTS: 12 of 16 patients showed complete remission (no recurrence of a detectable effusion). 3 patients showed a partial remission (recurrence of non-drainage-dependent effusion) (CR + PR = 94%). Within the mean follow-up period of 189 days no recurrences occurred. The rate of side effects was low. CONCLUSION: Intrapericardial instillation of mitoxantrone is a feasible and effective palliative method for the control of malignant pericardial effusions with little strain on the patients, short duration of hospital stay, cytotoxic characteristics of the substance with a correspondingly high rate of response and low side effects.

Adult↗