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Biomedical subjects

S Koch

Publications and source records attributed to S Koch.

228 records · Page 13Linked to original sources
PubMedDate not supplied

[Healing of osteochondral transplants--animal experiment studies using a sheep model].

AIM: Autologous grafting has developed into one of the preferred methods of treatment for focal osteochondral lesions, although basic research on this topic remains sparse. In an animal study, questions regarding the healing of such osteochondral transplants are clarified. METHOD: An autologous osteochondral transplantation was performed on the ovine knee using the standard operative protocol. Two groups, consisting of 10 sheep each, were evaluated after 3 and 6 months, respectively. RESULTS: During the clinical evaluation of the specimens, neither osteophytes nor synovial changes were observed. The consistency of the cartilaginous tissue began to reach a level equivalent to the surrounding tissue only after 6 months. Macroscopically, the superficial border of the transplanted osteochondral plug could easily be outlined at both time points. Radiographically, a solid osteointegration of the graft could already be documented at 3 months. In contrast, integration of the chondral surface of the OAT was not seen macro- or microscopically at any point in time. A firm physical interdigitation of the reconstructed joint surface could not be demonstrated. CONCLUSIONS: The lack of integration of the cartilaginous portion of the transplanted plugs into the reconstructed joint surface leads to questions regarding the long-term survival of the joint itself.

Animals↗
PubMedDate not supplied

The malignant potential of teratomas in infancy and childhood: the MAKEI experiences in non-testicular teratoma and implications for a new protocol.

UNLABELLED: Since 1982, mature and immature teratomas have been recruited into the MAHO and MAKEI protocols of the German Society for Pediatric Oncology and Hematology (GPOH) for testicular and non-testicular germ cell tumors in order to study the epidemiology and clinical behaviour of teratomas. Patients were registered in the epidemiologic German Childrens Cancer Registry and the GPOH Childrens Tumor Registry for pathological review. Patients with immaturity grade 2 and 3 according to Gonzales-Crussi were eligible for adjuvant chemotherapy. The consecutive protocols MAKEI 83/86/89 have been published previously in detail (Klin Paediatr 1997; 209: 228-234, Med Pediat Oncol 1998; 31: 8-15) and will be compared to the data of MAKEI 96. For this comparison, 274 patients from MAKEI 83/86/89 and 261 patients from MAKEI 96 are evaluable. RESULTS: 1) EFS after complete tumor resection has been estimated to 0.96 +/- 0.01 in both observation periods. 2) Incomplete tumor resection remains the main risk factor for relapse (EFS 0.55 +/- 0.09). 3) The relapse rate declined from 13.9 % in MAKEI 83/86/89 to 9.5 % in MAKEI 96. 4) In MAKEI 83/86/89 four newborns with teratoma died due to perioperative complications and nine children as a result of tumor progression, whereas in MAKEI 96 no newborn died, only one child died from tumor progression, and another child died during long time observation for another reason (meningitis). 5) In accordance to the experience of the MAKEI 83/86/89 studies, no child of the MAKEI 96 study presented with yolk sac tumor at recurrence if adjuvant chemotherapy was administered during first-line treatment because of immaturity. In contrast, more than half of the children with tumor recurrence after watch and wait strategy had yolk sac tumor in addition to teratoma.

Adolescent↗
PubMedDate not supplied

[Corrective osteotomies of the lower extremities following posttraumatic deformities].

PURPOSE: As part of a retrospective analysis of posttraumatic malunions of the lower extremity, the causes for deformity, as well as indications and methods for corrective osteotomies are reviewed. METHODS: From January 1992 until December 1996, a total of 115 patients underwent corrective osteotomies of the lower extremity secondary to posttraumatic deformities. The 89 adult patients with tibial (n = 54) or femoral (n = 35) malunion were analyzed as part of this study. RESULTS: The primary fracture treatment consisted of an intramedullary stabilization in 19 instances, a plate osteosynthesis in 22 and an external fixateur in 14 cases. Other forms of treatment were choosen in the remaining (n = 34) instances. Torsional deformities were seen after primary intramedullary nailings, while plate osteosynthesis lead to angulation in the frontal plane in the majority of the treated patients. In 43 instances uniplanar and in 46 cases multiplanar deformities had to be corrected. The correction was carried out with the help of an Ilisarow-ring fixator in 37 instances. As an internal stabilizer, 9 nails, 2 dynamic compression screws and 38 AO-plates were used. A bone graft was carried out primarily 33 times. CONCLUSIONS: The review of the literature, as well as of our own results, shows that deformities in the frontal plane should be corrected if they exceed 10 degrees of varus or 15 degrees of valgus. Malunions of more than 15 degrees in the sagittal and 15-20 degrees in the transverse plane should also be considered for correction, while a shortening of more than 3 cm represents an indication for corrective osteotomy. Callus distraction techniques have proven valuable in the correction of posttraumatic malunions of the lower leg, especially when soft tissue compromise is evident.

Adolescent↗
PubMedDate not supplied

High throughput encapsulation of murine fibroblasts in alginate using the JetCutter technology.

The JetCutter technology originally developed for high-throughput encapsulation of particles and substances into small beads was applied in this study for the entrapment of mammalian cells in alginate beads. In contrast to other established techniques such as the air jet droplet generation or laminar jet break-up, the JetCutter is capable of working with highly viscous fluids necessary for the production of stable beads based on hydrogels. A 1.5% (w/v) sodium alginate solution containing 2.0 x 106 murine fibroblasts/ml was processed under good manufacturing practice (GMP) conditions to beads with a mean diameter of 320 microm. The production capacity of the JetCutter technology was 5200 beads/s or to approximately 330 ml bead suspension per h. Beads were coated with poly-L-lysine and with an additional alginate layer to produce hollow microcapsules containing living cells. The influence of this method of encapsulation on the cell viability and morphology was investigated by light microscopic techniques. Encapsulated cells showed unchanged rates of proliferation and preserved morphology. They were able to survive in culture for extended periods of time. In conclusion, the JetCutter technology seems to be well suitable for alginate bead encapsulation of living mammalian cells.

Alginates↗
PubMedDate not supplied

Alginate encapsulation of genetically engineered mammalian cells: comparison of production devices, methods and microcapsule characteristics.

PRIMARY OBJECTIVE: Microencapsulation is a novel method for in vivo immunoprotection of genetically engineered mammalian cells. This study aimed at optimizing alginate/poly-l-lysine/alginate (APA) microencapsulation of mammalian cells in small size (< 300 microm) hollow core microcapsules and at evaluating some of the physical characteristics of APA microcapsules produced by different devices and with different alginate preparations. METHODS AND PROCEDURES: Alginate preparations with higher or lower viscosity were used with three different methods: (i) vibrating nozzle, (ii) coaxial gas flow extrusion (AirJet) and (iii) laminar jet break-up (JetCutter). Parameters and device settings for the production of microcapsules with specific characteristics were defined for all three methods. Mechanical stability of APA microcapsules and cell viability of encapsulated cells were investigated in long-term culture and in an animal model. MAIN RESULTS: Uniform spherical beads with a mean diameter < 300 microm could be produced by all three encapsulation methods. For the production of uniform microcapsules with a small diameter (< 300 microm) the vibrating nozzle technique required a relatively low viscosity of alginate (< 0.2 Pa/s), while the AirJet and JetCutter devices performed equally well with alginate of higher viscosity. In all cases, alginate with a lower molar mass was inferior to higher molar mass alginate in terms of mechanical stability of the microcapsules. Microcapsules with optimized mechanical properties were injected intravascularly in rats and shown to maintain their shape and the viability of encapsulated cells. CONCLUSIONS: The described methods and devices are able to produce APA microcapsules of small size and uniform shape which are mechanically stable in culture and may maintain the viability of the enclosed cells over extended periods of time. These microcapsules seem to be suitable for further therapeutic studies in an animal model of human disease.

Alginates↗
PubMedDate not supplied

Unexpected functions of FcepsilonRI on antigen-presenting cells.

In contrast to mast cells and basophils, the high affinity IgE receptor (FcepsilonRI) on antigen-presenting cells (APC) shows structural and functional differences. It consists only of a minimal structure of one alpha- and two gamma-chains and enables APC to efficiently take up and present antigen in IgE-mediated delayed-type hypersensitivity reactions that are thought to play a pivotal role in atopic diseases. However, recent studies of FcepsilonRI signal transduction and function on APC suggest additional mechanisms by which FcepsilonRI engagement on APC could affect inflammatory reactions. FcepsilonRI ligation is able to induce major signaling events like protein tyrosine kinase activation including p72(syk) leading to PLC-gamma1 phosphorylation and consecutive calcium influx. Late signaling events like the activation of transcription factors such as NF-kappaB provide a link to the release of proinflammatory cytokines and chemokines, Th-polarizing factors such as IL-12 and the induction of antiapoptotic factors. FcepsilonRI-mediated IL-10 production in monocytes could also influence their differentiation. Since there are hints that in vivo a functional FcepsilonRI signaling pathway only exists in individuals from an atopic background, we suggest that these unexpected mechanisms may have an effect on inflammatory reactions in atopic diseases.

Antigen-Presenting Cells↗
PubMedDate not supplied

Sonographic prenatal diagnosis of ambiguous genitalia.

A case report is presented herein of a 33-year-old woman with a history of congenital adrenal hyperplasia in 2 prior births. At 30 weeks of gestation, a scan of the fetal perineum demonstrated ambiguous genitalia which was confirmed at birth. This case demonstrates that when the fetal perineum is well visualized, the diagnosis of normal and abnormal genital development can be made sonographically. This can assist in perinatal/neonatal management, planning and in some cases, can also serve as an additional tool to monitor the success of prenatal steroid therapy of fetal congenital adrenal hyperplasia.

Adrenal Hyperplasia, Congenital↗
PubMedDate not supplied

First-trimester needle embryofetoscopy and prenatal diagnosis.

OBJECTIVE: To demonstrate the efficacy of first-trimester needle embryofetoscopy (or embryoscopy) for prenatal diagnosis in a continuing pregnancy. STUDY DESIGN: A patient at risk for giving birth to an infant with Robert's syndrome was referred for prenatal diagnosis at 12 weeks of gestation. RESULTS: Transabdominal embryoscopy and amniocentesis were performed. Direct visualization of the embryo was achieved and no gross limb or facial abnormalities were seen. Chromosome studies of the amniotic fluid revealed a normal male 46, XY. Special studies with C-banding and DAPI techniques revealed no evidence of premature separation of centromeres. Two- and three-dimensional ultrasound also demonstrated no gross limb or facial abnormalities. CONCLUSIONS: This case confirms the efficacy of embryoscopy as a simple and relatively low-risk approach to first-trimester diagnosis for continuing pregnancies.

Adult↗
PubMedDate not supplied

[Detection of microembolus with transcranial doppler].

OBJECTIVES: To review techniques and the most important clinical applications of microembolus detection with transcranial Doppler. DEVELOPMENT: Technical aspects of microembolus detection are discussed initially; clinical circumstances in which embolus detection is currently used follow, such as carotid stenosis, cardiac pathology, monitoring during neuroangiography, coronary revascularization surgery and endarterectomy. Lastly, the potential clinical applications of this technique are reviewed: localization of an embolic source, risk of recurrent ischemia in patients with unstable atherosclerotic plaques, intraoperative monitoring and potential surgical technique modifications based on this information, contributions to the understanding of the pathophysiology of the fat embolism syndrome, and monitoring therapeutic efficacy of antithrombotics and thrombolytics. CONCLUSIONS: The ability to detect cerebral emboli with transcranial ultrasound has increased significantly our understanding about the pathogenesis of cerebral ischemia. Microembolus detection with transcranial Doppler is a powerful and novel diagnostic technique that allows to study the embolic process in vivo and in real time, instead of using indirect indicators of embolism (clinical and radiological features, possible embolic sources, etc.).

Brain Ischemia↗
PubMedDate not supplied

Diffusion-weighted imaging shows cytotoxic and vasogenic edema in eclampsia.

In eclampsia, MR imaging shows reversible T2 hyperintensities in a parietal and occipital distribution. Findings on diffusion-weighted images suggest that these abnormalities are areas of vasogenic edema. We describe the presence of both cytotoxic and vasogenic edema, as detected by diffusion-weighted imaging, in a woman with eclampsia. Follow-up MR imaging showed that the regions of cytotoxic edema progressed to cerebral infarction. This case suggests that diffusion-weighted imaging allows the early detection of ischemic infarcts in patients with eclampsia.

Adult↗
PubMedDate not supplied

Cytokines, cytokine antagonists and soluble adhesion molecules in patients with ocular Behçet's disease treated with human recombinant interferon-alpha2a. Results of an open study and review of the literature.

OBJECTIVE: To elucidate the influence that interferon-alpha exerts on the cytokine network in active ocular Behçet's disease (BD). METHODS: Fifty patients with active ocular BD were treated with human recombinant interferon-alpha2a (rhIFN-alpha2a). Serum was analysed for the presence of IL-10, TNF-alpha, IL-8, IL-6, sIL-2R, IFN-gamma, IFN-alpha, IL-12, IL-4, sTNFRI (p55), sTNFRII (p75), IL-1RA, G-CSF, sE-selectin, sVCAM-1, sICAM-1 and neopterin before initiation of and at several time points during IFN treatment and compared to 21 healthy controls. RESULTS: The levels of IFN-alpha IL1-RA and sTNFRII were significantly increased in the patients at baseline in comparison to healthy controls. During treatment with rhIFN-alpha2a, when remission was achieved as defined by the scoring system used, a significant increase in levels of IFN-alpha, IL-2R, TNF-alpha, sTNF-RII, sICAM-1, sVCAM-1, neopterin in the serum was observed, with a tendency towards increased IL-1RA as well. In contrast, leuko- and thrombocyte counts and sE-selectin serum levels significantly decreased. Positive correlations were found between IFN dosage or serum levels and sVCAM-I, neopterin, sTNF-RII and sIL-2R, between sVCAM-1, sIL-2R, TNF-alpha, sTNF-RII and neopterin, sICAM-I and sVCAM-1, sIL2-R and sTNF-RII, and, finally, between sIL2-R and sICAM-I. CONCLUSIONS: IFN-alpha exerts diverse influences mainly on cytokine antagonists and soluble adhesion molecules. Because sTNF-RII and IL-1RA were increased by IFN-alpha treatment, these might be interesting alternative treatment options in refractory BD. Some of the side-effects of IFN-alpha may be caused by activation of monocytes, which is reflected by an increase in neopterin serum levels.

Antiviral Agents↗