Biomedical subjects

F Koch

Publications and source records attributed to F Koch.

At least 19 recordsLinked to original sources

PubMed2006

Abscess of the orbit arising 48 h after root canal treatment of a maxillary first molar.

AIM: To discuss a rare, but severe complication arising following routine root canal treatment. SUMMARY: An orbital abscess is reported that occurred following routine root canal treatment. A young, healthy female patient, with no history of chronic paranasal infection had undergone root canal treatment of the right maxillary first molar. On hospital admission, she presented with extensive periorbital swelling and discreet diplopia. Computed tomography imaging identified massive purulent sinusitis and subsequent involvement of the orbit via the inferior and medial orbital wall within 48 h after completion of root canal treatment. Immediate surgical drainage of the maxillary sinus and the orbit was established and a high dose of perioperative antibiotics (Amoxicillin/Clavulanic acid, Gentamycin, Metronidazole) were administered. Vision remained undisturbed and mobility of the globe recovered within 10 days. KEY LEARNING POINTS: Rapid exacerbation of a periapical inflammation may occur following root canal treatment and may even involve the orbit. A typical speed of disease progression or ophthalmic symptoms should alert the clinician to at least consider unusual early orbital spread of odontogenic infection. When extra-alveolar spread and especially orbital spread is suspected, immediate referral to a maxillofacial or other specialized unit is mandatory.

Abscess↗

PubMed2005

Direct intralymphatic injection of peptide vaccines enhances immunogenicity.

Research to enhance the efficiency of vaccines focuses mainly on improving either the adjuvant or the type and form of the antigen. This study evaluates the influence of the administration route on the efficiency of a peptide-based vaccine. Peptide vaccines are generally administered subcutaneously or intradermally, from where they must reach secondary lymphatic organs to induce an immune response. We analyzed the efficacy of peptide vaccines administered directly into a lymph node. Using a MHC class I-binding peptide from lymphocytic choriomeningitis virus, we found that intralymphatic injection enhanced immunogenicity by as much as 10(6) times when compared to subcutaneous and intradermal vaccination. Intralymphatic administration induced CD8 T cell responses with strong cytotoxic activity and IFN-gamma production that conferred long-term protection against viral infections and tumors. These results should have immediate implications for clinical immunotherapy of infectious disease and cancer.

Animals↗

PubMed2004

In situ analysis of metal melts in metallurgic vacuum devices by laser-induced breakdown spectroscopy.

We report on rapid in situ analysis of liquid metal melts under reduced ambient pressure by laser-induced breakdown spectroscopy (LIBS) using a transportable system. LIBS denotes a method in which characteristic optical emission line intensities of excited species in laser-generated plasma plumes are used for a quantitative chemical analysis of target materials. It is a fast, noncontact method that can be carried out under various atmospheric conditions, allowing large working distances between the sample under investigation and the detection system. For these reasons, LIBS is applicable in particular for process control in metallurgy under reduced ambient pressure. This was demonstrated for two types of vacuum devices under production conditions at a steel mill. The results of these experiments, including calibration curves for Cr, Ni, and Mg in liquid steel, are presented. The influence of variations in the ambient pressure on the results of the LIBS analysis is discussed within the frame of a generalized shock-wave model for the expansion of the laser-induced plasma plume.

Journal Article↗

PubMed2002

Stimulated light emission in dense fog confined inside a porous glass matrix.

We report on light amplification through stimulated emission in a dielectrically disordered medium. Liquid fragments confined in the solid matrix of porous quartz layers result in a random fluctuation of the dielectric function, and dye molecules embedded in the voids yield optical gain. The level of opacity is tunable by the ambient vapor pressure of the dielectric substance. In the multiple scattering regime, a strong intensity enhancement of the dye emission accompanied by significant spectral narrowing is observed above the threshold for a layer being in the opalescence state.

Journal Article↗

PubMed2002

Resonant electronic energy transfer from excitons confined in silicon nanocrystals to oxygen molecules.

We demonstrate efficient resonant energy transfer from excitons confined in silicon nanocrystals to molecular oxygen (MO). Quenching of photoluminescence (PL) of silicon nanocrystals by MO physisorbed on their surface is found to be most efficient when the energy of excitons coincides with triplet-singlet splitting energy of oxygen molecules. The dependence of PL quenching efficiency on nanocrystal surface termination is consistent with short-range resonant electron exchange mechanism of energy transfer. A highly developed surface of silicon nanocrystal assemblies and a long radiative lifetime of excitons are favorable for achieving a high efficiency of this process.

Journal Article↗

PubMed2001

Strong explosive interaction of hydrogenated porous silicon with oxygen at cryogenic temperatures.

We report new types of heterogeneous hydrogen-oxygen and silicon-oxygen branched chain reactions which have been found to proceed explosively after the filling of pores of hydrogen-terminated porous silicon (Si) by condensed or liquid oxygen in the temperature range of 4.2-90 K. Infrared vibrational absorption spectroscopy shows that, while initially Si nanocrystals assembling the layers have hydrogen-terminated surfaces, the final products of the reaction are SiO2 and H2O. Time-resolved optical experiments show that the explosive reaction develops in a time scale of 10(-6) s. We emphasize the remarkable structural properties of porous Si layers which are crucial for the strong explosive interaction.

Journal Article↗

PubMed2001

Cross reactivity of three T cell attracting murine chemokines stimulating the CXC chemokine receptor CXCR3 and their induction in cultured cells and during allograft rejection.

Recent work identified the murine gene homologous to the human T cell attracting chemokine CXC receptor ligand 11 (CXCL11, also termed I-TAC, SCYB11, ss-R1, H174, IP-9). Here, the biological activity and expression patterns of murine CXCL11 relative to CXCL9 (MIG) and CXCL10 (IP-10/crg-2), the other two CXCR3 ligands, were assessed. Calcium mobilization and chemotaxis experiments demonstrated that murine CXCL11 stimulated murine CXCR3 at much lower doses than murine CXCL9 or murine CXCL10. Murine CXCL11 also evoked calcium mobilization in CHO cells transfected with human CXCR3 and was chemotactic for CXCR3-expressing human T lymphocytes as well as for 300--19 pre-B cells transfected with human or murine CXCR3. Moreover, murine CXCL11 blocked the chemotactic effect of human CXCL11 on human CXCR3 transfectants. Depending on cell type (macrophage-like cells RAW264.7, J774A.1, fetal F20 and adult dermal fibroblasts, immature and mature bone marrow-derived dendritic cells) and stimulus (interferons, LPS, IL-1 beta and TNF-alpha), an up to 10,000-fold increase of CXCL9, CXCL10 and CXCL11 mRNA levels, quantified by real-time PCR, was observed. In vivo, the three chemokines are constitutively expressed in various tissues from healthy BALB/c mice and were strongly up-regulated during rejection of allogeneic heart transplants. Chemokine mRNA levels exceeded those of CXCR3 and IFN-gamma which were induced with similar kinetics by several orders of magnitude.

Animals↗

PubMed2001

Migration of dendritic cells into lymphatics-the Langerhans cell example: routes, regulation, and relevance.

Dendritic cells are leukocytes of bone marrow origin. They are central to the control of the immune response. Dendritic cells are highly specialized in processing and presenting antigens (microbes, proteins) to helper T lymphocytes. Thereby, they critically regulate further downstream processes such as the development of cytotoxic T lymphocytes, the production of antibodies by B lymphocytes, or the activation of macrophages. A new field of dendritic cell biology is the study of their potential role in inducing peripheral tolerance. The immunogenic/tolerogenic potential of dendritic cells is increasingly being utilized in immunotherapy, particularly for the elicitation of antitumor responses. One very important specialization of dendritic cells is their outstanding capacity to migrate from sites of antigen uptake to lymphoid organs. Much has been learned about this process from studying one particular type of dendritic cell, namely, the Langerhans cell of the epidermis. Therefore, the migratory properties of Langerhans cells are reviewed. Knowledge about this "prototype dendritic cell" may help researchers to understand migration of other types of dendritic cells.

Animals↗

PubMed2001

Interleukin-16 supports the migration of Langerhans cells, partly in a CD4-independent way.

Migration of cutaneous dendritic cells is essential for the induction of primary immune responses. Chemotaxis plays an important part in guiding migrating cells through the skin. Therefore, we investigated the influence of interleukin-16, a potent chemoattractant, on the migratory properties of cutaneous dendritic cells. Interleukin-16 added to murine and human skin explant cultures, enhanced emigration of Langerhans cells as well as dermal dendritic cells out of the skin. In contrast to tumor necrosis factor-alpha, intradermally injected interleukin-16 did not reduce the density of Langerhans cells suggesting a chemotactic rather than a mechanistic migration-inducing effect of interleukin-16. In support of these findings, the known migration-promoting effect of tumor necrosis factor-alpha in skin explant cultures could be neutralized by anti-interleukin-16 antibody and vice versa, indicating different but cooperative ways of action for both cytokines. In whole skin explant cultures blocking of the interleukin-16 effect was also achieved with a monoclonal antibody against CD4, the receptor for interleukin-16. In contrast, in cultures of murine epidermis alone no blocking by anti-CD4 became obvious and in CD4-deficient mice Langerhans cell migration in response to interleukin-16 was maintained. This suggests that another receptor for interleukin-16 might be operative for Langerhans cells in the mouse epidermis. Finally, we detected interleukin-16-positive cells in the dermis of skin explants, tumor necrosis factor-alpha-treated and contact allergen-treated skin. Taken together, it seems likely that locally secreted interleukin-16 might serve to enhance the migration of cutaneous dendritic cells and optimize the response to foreign antigen encountering the skin.

Animals↗

PubMed2001

[Effect of retinal coagulation status on oxidative metabolite and VEGF in 208 patients with proliferative diabetic retinopathy].

BACKGROUND: Oxidative metabolites and different cytokines are believed to be involved in the pathogenesis of (proliferative) diabetic retinopathy. It was the aim of this study to analyze vitreous body and proliferations of diabetic patients for oxidative metabolites and VEGF und to correlate these values to the retinal coagulation status. PATIENTS AND METHODS: The study was performed in 208 patients vitrectomized for diabetic retinopathy (Type I: n = 114, Type II: n = 94). Grouping of patients was performed according to retinal coagulations status: (1) no or minimal preoperative coagulation [mean coagulation area, CA: 156 mm2], (2) coagulation (scatter laser coagulation und/oder cryopexy) < 3 months before surgery [CA: 589 mm2]. (3) coagulation > 3 months before surgery [CA: 546 mm2]. In the vitreous body and, if present, in the fibrovascular proliferations (Type I: n = 83; Type II: n = 73) the level of lipid peroxides (LPO, measured with two methods) and VEGF was determined. RESULTS: In the vitreous body LPO in group 1 were significantly (P < 0.01 (Type I und II)) higher as compared to other groups. In group 3 LPO were significantly lower as compared to group 2 (P < 0.01 (Typ I) and P < 0.05 (Typ II)). Similar results were observed in the proliferations. In Type I patients VEGF values were significantly (P < 0.01 for group 1 vs. 2 and groups 1/2 vs. 3) reduced following coagulation and coagulation + 3 months. In Type II patients only group 3 was significantly (P < 0.01) different from group 1. In proliferations groups 2 and 3 were significantly different from group 1 (P < 0.05 for Typ I and Type II patients). CONCLUSIONS: The time course of the values leads to the conclusion that oxidative metabolites are able to directly modulate growth activity and to exert this effect via induction of VEGF. This hypothesis has to be confirmed in vitro and by means of a prospective study.

Diabetes Mellitus↗

PubMed2000

Ordering and self-organization in nanocrystalline silicon

The spontaneous formation of organized nanocrystals in semiconductors has been observed during heteroepitaxial growth and chemical synthesis. The ability to fabricate size-controlled silicon nanocrystals encapsulated by insulating SiO2 would be of significant interest to the microelectronics industry. But reproducible manufacture of such crystals is hampered by the amorphous nature of SiO2 and the differing thermal expansion coefficients of the two materials. Previous attempts to fabricate Si nanocrystals failed to achieve control over their shape and crystallographic orientation, the latter property being important in systems such as Si quantum dots. Here we report the self-organization of Si nanocrystals larger than 80 A into brick-shaped crystallites oriented along the (111) crystallographic direction. The nanocrystals are formed by the solid-phase crystallization of nanometre-thick layers of amorphous Si confined between SiO2 layers. The shape and orientation of the crystallites results in relatively narrow photoluminescence, whereas isotropic particles produce qualitatively different, broad light emission. Our results should aid the development of maskless, reproducible Si nanofabrication techniques.

Journal Article↗

PubMed2000

L-Arginine-nitric oxide pathway-related metabolites in the aqueous humor of diabetic patients.

PURPOSE: Nitric oxide (NO) is an important signal-transduction molecule that plays a significant role in the regulation of cardiovascular functions. In the L-arginine-NO pathway, NO synthase (NOS) converts L-arginine (L-Arg), the only known biologic substrate for NO formation, to NO and L-citrulline (L-Cit). Excessive NO production mediated by the inducible isoform of NOS has been implicated in the pathogenesis of various diseases. In the present study it was hypothesized that in vitreoretinal disorders such as diabetic retinopathy the production of L-Arg-NO pathway-related metabolites may be upregulated as a result of increased NO generation. METHODS: From 20 eyes of nondiabetic subjects and 22 eyes of diabetic patients with (n = 14) and without (n = 8) diabetic retinopathy, undiluted samples of aqueous humor were drawn before cataract surgery. Levels of L-Arg, L-Cit, and the specific NOS by-product N(G)-hydroxy-L-arginine (HOArg) were measured by high-performance liquid chromatography. RESULTS: L-Arg, L-Cit, and HOArg were detected in all aqueous humor samples from diabetic and nondiabetic patients (n = 42). Comparison of HOArg levels in nondiabetic and diabetic subjects showed significantly higher levels in diabetic patients (P = 0.002). Concentrations of HOArg were higher in samples from patients with (P = 0.005) and without diabetic retinopathy (P = 0.033) than in control subjects. No statistically significant differences were observed in L-Arg or L-Cit levels. CONCLUSIONS: Elevated levels of HOArg in the aqueous humor of diabetic patients reflect the possible role of NO as a significant factor in the regulation of retinal vascular functions and intraocular proliferative changes in diabetes mellitus in vivo. The control of intraocular NO production may constitute a potential therapeutic approach in diabetic retinopathy.

Aged↗

PubMed1999

M1204, a novel 2',5' oligoadenylate synthetase with a ubiquitin-like extension, is induced during maturation of murine dendritic cells.

A novel molecule expressed by spleen dendritic cells (DC) was isolated using a subtractive hybridization approach. The full-length M1204 clone has 3063 bp, with 1415 bp spanning a single open reading frame, coding for a protein of a predicted size of about 50 kDa. This sequence has strong homology to 2', 5' oligoadenylate synthetase and contains a ubiquitin-like domain. In Northern blot analyses the mRNA is strongly expressed in spleen DC, whereas, in bone marrow-derived DC, the amount of mRNA increases during the maturation process. None of the other leukocytes nor several hemopoietic cell lines tested express this mRNA, but clear expression occurs in many organs, the highest levels being in thymus, lung, and bone marrow. In situ hybridization, combined with immunocytochemical staining of tissue sections of lung and spleen, shows colocalization of M1204 with the 2A1 and NLDC DC markers. In Western blot experiments, an antiserum raised against the recombinant M1204 recognizes a single band in bone marrow-derived DC and in the lung. The expressed oligoadenylate synthetase domain is active in synthesizing 2',5' diadenylate, which by itself may inhibit viral protein synthesis and may also function as a substrate for 2',5' oligoadenylate synthetase. Since the oligoadenylate/RNase L system provides early protection against virus infection, we hypothesize that M1204 prevents virus-induced cell death in DC.

2',5'-Oligoadenylate Synthetase↗

PubMed1999

An advanced culture method for generating large quantities of highly pure dendritic cells from mouse bone marrow.

As dendritic cells (DC) are rare populations in all organs, their generation from hematopoietic precursors in large quantities has proven critical to study their biology. From murine bone marrow about 5 x 10(6) cells at 70% purity are obtained per mouse after 8 days of culture with GM-CSF. We have improved this standard method and routinely achieve a 50-fold higher yield, i.e., 1-3 x 10(8) immature and mature DC per mouse at 90-95% purity. The major modifications were: (i) the avoidance of any active depletion of bone marrow cell subpopulations to circumvent loss of precursors, (ii) a lower plating density of bone marrow cells, (iii) a prolonged culture period of 10-12 days, (iv) the reduction of the GM-CSF dose from day 8 or 10 onwards to reduce granulocyte contaminations. The final non-adherent population at day 10-12 constitutes a mixture of immature and mature DC. Further maturation of DC could be induced by high doses of LPS or TNF-alpha for the last 24 h, where 50-70% of the non-adherent fraction represented mature DC with high levels of NLDC-145, CD86 and CD40. This method allows by simple means the generation of high numbers of murine DC with very low B cell or granulocyte contaminations. It will be valuable to study DC biology notably at the molecular level.

Animals↗

PubMed1999

Enhancing perioperative nursing effectiveness through informatics.

The science of nursing informatics is becoming increasingly important to delivering quality nursing care to all patient populations. Perioperative nursing informatics skills are practiced within the context of powerful and complex information systems that enhance nurses' ability to view and report clinical data in a manner that has never before been possible. This article explores how the analysis of several examples of two typical system indicators (i.e., the unplanned returns to surgery rate within the same admission event, surgical site infection rate) can result in improved patient outcomes. Nursing informatics is an invaluable tool for identifying trends and communicating them to perioperative nurses in a way that can positively influence the delivery of perioperative care and patient outcomes.

Database Management Systems↗

PubMed1999

Migration of langerhans cells and dermal dendritic cells in skin organ cultures: augmentation by TNF-alpha and IL-1beta.

Migration from sites of antigen encounter to lymphoid organs is essential to the strong immunogenic function of dendritic cells (DC). In the skin, migration proceeds through dermal lymphatic vessels and is regulated in an incompletely understood way by inflammatory mediators. We studied the effects of tumor necrosis factor alpha (TNF-alpha) and interleukin-1beta (IL-1beta) in mouse skin organ cultures by direct enumeration of migrating DC and by immunohistochemistry. (1) Neutralizing antibodies to TNF-alpha and IL-1beta inhibited migration of DC, also in human skin explants (TNF-alpha). (2) TNF-alpha at low concentrations (50 U/mL) and IL-1beta (50-3000 U/mL) augmented migration to about 150% of spontaneous migration. (3) High concentrations of TNF-alpha (5000 U/mL) inhibited migration by approximately 50%. (4) DC migration from skin explants of TNF-alpha/lymphotoxin-alpha double-deficient mice and TNF-receptor type 1 and 2 double knockout mice was not impaired. (5) TNF-alpha effects were neutralized by anti-IL-1beta, and vice versa. We conclude that in normal animals both TNF-alpha and IL-1beta are required for DC migration to occur. In the complete absence of one cytokine (TNF-alpha), however, backup mechanisms step in.

Animals↗

PubMed1998

Effects of perfluorooctylbromide and vitamin E on ischemia induced retinal oxidative tissue damage.

The aim of this study was to investigate the extent to which ischemia and reperfusion lead to oxidative damage of the retinal tissue and investigate how ischemic and reperfused retinal tissues react to the application of perfluorooctylbromide (PFOB) and, if this reaction can be influenced by protective drugs such as vitamin E (Vit.E). The experiments were performed with 60 male Wistar rats, divided into 12 groups using an established model of reversible ischemia and reperfusion of the globe. Grouping of animals was carried out according to different ischemia and reperfusion periods and different therapeutic regimens (PFOB, Vit.E). Treatment with PFOB and/or Vit.E was performed after 60 min of ischemia with 60 min of reperfusion. At the end of the experiments thiobarbituric acid reactive substances (TBARS) were determined in the retinal tissues and served as parameters of oxidative tissue damage. Ischemia of up to 60 min led to a significant increase in TBARS values. Ninety and 120 min of ischemia led to no further significant elevation compared to the 60 min or 90 min group. Following 60 min of ischemia, a reperfusion period of 15 min led to an increase in TBARS values that was significant (P<0.05) after 30 and 60 min. Addition of PFOB resulted in a further significant (P<0.05) increase in TBARS values as compared to the respective group without treatment. Vit. E alone did not change the values significantly compared to the respective group without treatment. However, the application of Vit.E in addition to PFOB led to a significant reduction in TBARS values. Ischemia resulted in severe oxidative retinal tissue damage, which increased during reperfusion. The reperfusion damage might be due to the known depletion of protecting substances such as vitamin E. Enhancement of oxygen supply by PFOB during reperfusion without any tissue protection leads to more severe damage. Thus, additional protection of the tissue by powerful antioxidants is necessary when providing oxygen for better tissue recovery.

Animals↗

PubMed1998

[The effects of low-dose Co-60 irradiation on the course of aseptic arthritis in a rabbit knee joint].

PURPOSE: Numerous clinical observations demonstrate the efficacy of low radiation doses in the treatment of painful osteoarthritis. Experimental investigations remain scarce. We investigated the effects of locally daily 5 times 1.0 Gy 60-Co irradiation on an artificially induced aseptic gonarthritis in rabbits. MATERIAL AND METHODS: Three separate experiments (EV) were performed (10 rabbits per experiment, 5 treated/5 controls; duration: EV1: 18 days; EV2: 6 days; EV3: 29 days). An aseptic arthritis in the right knee joint of rabbits was induced by intraarticular injection of 0.5 ml papain solution (3%, 30,000 USP/mg) on day 0. The arthritic knee joint of the anesthesized animals was irradiated daily from day 1 to 5 with 5 times 1.0 Gy. The controls were sham-irradiated under the same conditions. The time course of arthritis in treated animals and sham-treated controls was evaluated by clinical, laboratory-chemical and histological criteria. The clinical investigation was performed daily, the puncture of the knee-joints was carried out several times in EV1, and at the end of experiments in EV2 and EV3. At the end of the observation period, animals were killed and the knee joints excised for histological analysis. RESULTS: The intraarticular injection of papain caused a peracute inflammatory response in all animals. After 1 week the chronic stage was reached, and the experimental arthritis resolved slowly within several weeks. Local irradiation accelerated the decrease of inflammatory joint swelling, being significant by day 4. On day 6 the volume of synovial fluid in irradiated knee-joints was significantly smaller. The morphometric data indicated a reduction in thickness of synovial membrane, a decrease in number of synovial cell layers, and a decrease in distance between capillaries and the synovial membrane surface following irradiation of arthritic joints. Due to considerable individual variability, the morphometric data partially did not reach statistically significance. CONCLUSION: The experiments provide evidence for an antiphlogistic effect of irradiation with 5 times 1.0 Gy in vivo. They support the clinical observations of the efficacy of anti-inflammatory radiotherapy.

Animals↗