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Biomedical subjects

M Lohmann

Publications and source records attributed to M Lohmann.

At least 19 recordsLinked to original sources
PubMed2006

Qualitative evaluation of titanium implant integration into bone by diffraction enhanced imaging.

Diffraction enhanced imaging (DEI) uses refraction of x-rays at edges, which allows pronounced visualization of material borders and rejects scattering which often obscures edges and blurs images. Here, the first evidence is presented that, using DEI, a destruction-free evaluation of the quality of integration of metal implants into bone is possible. Experiments were performed in rabbits and sheep with model implants to investigate the option for DEI as a tool in implant research. The results obtained from DEI were compared to conventional histology obtained from the specimens. DE images allow the identification of the quality of ingrowth of bone into the hydroxyapatite layer of the implant. Incomplete integration of the implant with a remaining gap of less than 0.3 mm caused the presence of a highly refractive edge at the implant/bone border. In contrast, implants with bone fully grown onto the surface did not display a refractive signal. Therefore, the refractive signal could be utilized to diagnose implant healing and/or loosening.

Animals↗
PubMed2006

Development and investigation of a pollution control pit for treatment of stormwater from metal roofs and traffic areas.

Source control by on-site retention and infiltration of stormwater is a sustainable and proven alternative to classical drainage methods. Unfortunately, sedimentary particles and pollutants from drained surfaces cause clogging and endanger soil and groundwater during long-term operation of infiltration devices. German water authorities recommend the use of infiltration devices, such as swales or swale-trench-systems. Direct infiltration by underground facilities, such as pipes, trenches or sinks, without pretreatment of runoff is generally not permitted. Problems occur with runoff from metal roofs, traffic areas and industrial sites. However, due to site limitations, underground systems are often the only feasible option. To overcome this situation, a pollution control pit was developed with a hydrodynamic separator and a multistage filter made of coated porous concrete. The system treats runoff at source and protects soil, groundwater and receiving waterways. Typically, more than 90% of the pollutants such as sedimentary particles, hydrocarbons and heavy metals can be removed. Filters have been developed to treat even higher polluted stormwater loads from metal roofs and industrial sites. The treatment process is based on sedimentation, filtration, adsorption and chemical precipitation. Sediments are trapped in a special chamber within the pit and can be removed easily. Other pollutants are captured in the concrete filter upstream of the sediment separator chamber. Filters can be easily replaced.

Cities↗
PubMed2004

Safety and performance of a new non-adhesive foam dressing for the treatment of diabetic foot ulcers.

OBJECTIVE: This study aimed to document the safety and performance of a new non-adhesive foam dressing (Biatain Non-adhesive Dressing, Coloplast A/S) in the treatment of established foot ulcers in patients with diabetes. METHOD: This was an open non-comparative prospective study. Participants had an ankle brachial pressure index score of over 0.4 (neuro-ischaemic) and an ulcer bigger than 1 cm2 and less than 8 cm2 in any direction. The treatment period was six weeks. RESULTS: Thirty-five out of 37 patients completed the study. The mean wound area reduced from 5.4 cm2 to 2.5 cm2. Relative wound area reduced from 100% at baseline to 40% at week 6. 'Wearing comfort' improved throughout the study (p = 0.039). Maceration remained stable or improved. None of the four reported adverse events were device related. CONCLUSION: This study demonstrates that treatment of diabetic foot ulcers with Biatain Non-adhesive Dressing results in considerable wound area reduction and prevents any deterioration in maceration. The dressing is safe and effective in the management of these ulcers.

Activities of Daily Living↗
PubMed2003

Comparison of intravenous coronary angiography using synchrotron radiation with selective coronary angiography.

Intravenous coronary angiography with synchrotron radiation is a novel and minimally invasive technique for coronary imaging. At the Hamburger Synchrotronstrahlungslabor HASYLAB at DESY, a dedicated angiography system has been developed, which has been shown to provide detailed images of coronary artery segments. For each scan, two monochromatic X-ray images below and above the K-edge of iodine were recorded simultaneously. The two images were subtracted logarithmically to produce a maximal contrast enhancement of the iodine. To date, the procedure has been carried out on 379 outpatients. No complications occurred during or after the angiographic procedure, and hospitalization was not required in any subject. The acceptance by patient is extremely high. Five outside reviewers, blinded as to the clinical data or prior angiographic interpretation, reviewed the images for the presence or absence of 70% or more occlusion of a vessel. They reached a sensitivity of 79% and a specificity of 99%. The study has demonstrated that the synchrotron method has satisfactory sensitivity and very high specificity for severe stenoses. The new method has several advantages over magnetic resonance imaging (MRI), electron beam computed tomography (EBCT), and multi-slice computed tomography (MSCT). Neither vascular calcification (CT) nor the presence of metal stents (MRI) impairs the evaluation of perfusion of segments of the coronary arteries. Furthermore, the spatial resolution is three or four times higher using synchrotron angiography, and problems due to respiratory motion are eliminated.

Adult↗
PubMed2001

A new concept of a multidisciplinary wound healing center and a national expert function of wound healing.

HYPOTHESIS: An independent, multidisciplinary wound healing center in an accepted national expert function of wound healing is the optimal way to improve prophylaxis and treatment of patients with problem wounds. DESIGN: A clinical perspective analysis. SETTING: An independent, multidisciplinary wound healing center focusing on all types of problem wounds, organized as a university hospital department, and integrated in an expert function in the national health care organization of Denmark. PATIENTS AND METHODS: Patients with all types of problem wounds referred to and treated in the center during the first years of its existence provided a model for a new multidisciplinary structure for treatment of wound patients in the health care system. RESULTS: During the first 3 years of the fully functioning wound healing center, a total of 23 802 patient consultations were performed in the outpatient clinic, and 1014 patients with problem wounds were hospitalized in the inpatient ward. The surgical concept of the center has resulted in improved healing rates in patients with leg ulcers and decreased rates of major amputations. The outpatient function has resulted in a decrease in the number of patients transported in beds to the center. This structure provides better opportunities for basic and clinical research as well as for establishing expert education for all types of health care personnel. The center's structure has been the background for establishing an expert function in wound healing, allowing the wound healing area area to be fully integrated in the Danish National Health Care System. Overall, the concept and structure of the center have enhanced the knowledge and understanding of wound problems and increased the status of wound healing and patient care. CONCLUSIONS: Establishing multidisciplinary centers integrated into an accepted national expert function of wound healing is an optimal way to improve the clinical outcome of prophylaxis and treatment of all types of problem wounds. This model, with minor adjustments, may be applicable for both industrialized and developing countries.

Algorithms↗
PubMed2001

Sequestration of biological reactive intermediates by trapping as covalent enzyme-intermediate complex.

One important class of biological reactive intermediates arising in the course of human xenobiotic metabolism are arene and alkene oxides. The major safeguard against the potential genotoxic effects of these compounds is the microsomal epoxide hydrolase (mEH). This enzyme has a broad substrate specificity but--on the first sight--seems to be inadequately suited for this protection task due to its low turnover number with most of its substrates. The recent progress in the understanding of the mechanism of enzymatic epoxide hydrolysis has shed new light on this apparent dilemma: Epoxide hydrolases convert their substrates via the intermediate formation of a covalent enzyme-substrate complex, and it has been shown that the formation of the intermediate proceeds by orders of magnitudes faster than the subsequent hydrolysis, i.e. the formation of the terminal product. Thus, the enzyme acts like a molecular sponge by binding and inactivating the dangerous metabolite very fast while the subsequent product release is considerably slower, and quantification of the latter heavily underestimates the speed of detoxification. Usually, the slow enzyme regeneration does not pose a problem, since the mEH is highly abundant in human liver, the organ with the highest capacity to metabolically generate epoxides. Computer simulation provides evidence that the high amount of mEH enzyme is crucial for the control of the steady-state level of a substrate epoxide and can keep it extremely low. Once the mEH is titrated out under conditions of extraordinarily high epoxide concentration, the epoxide steady-state level steeply rises, leading to a sudden burst of the genotoxic effect. This prediction of the computer simulation is in perfect agreement with our experimental work. V79 Chinese Hamster cells that we have genetically engineered to express human mEH at about the same level as that observed in human liver are well protected from any measurable genotoxic effect of the model compound styrene oxide (STO) up to an apparent threshold level of 100 microM in the cell culture medium. In V79 cells that do not express mEH, STO triggers the formation of DNA strand breaks in a dose-dependent manner with no apparent threshold. Above 100 microM, the genotoxic effect of STO in the mEH-expressing cell line parallels the one in the parental cell line.

Animals↗
PubMed2001

Lysine and polyamines are substrates for transglutamination of Rho by the Bordetella dermonecrotic toxin.

Bordetella dermonecrotic toxin (DNT) catalyzes the transglutamination of glutamine-63/61 of Rho GTPases, thereby constitutively activating Rho proteins. Here we identified second substrates for transglutamination of RhoA by DNT. The enzymatically active fragment of DNT (residues 1136 to 1451, DeltaDNT) induced the incorporation of L-[(14)C]lysine in RhoA in a concentration-dependent manner. Also, Rac and Cdc42, but not Ras, were transglutaminated with lysine by DeltaDNT. Transglutamination of the GTPase with L-lysine inhibited intrinsic and Rho-GAP-stimulated GTP hydrolysis of RhoA. In contrast to lysine, treatment of RhoA with alanine, arginine, and glutamine were not able to substitute for lysine in the transglutamination reaction. DNT increased the incorporation of L-[(14)C]lysine into embryonic bovine lung cells. Microinjection of GST-RhoA together with the enzymatically active DNT fragment into Xenopus oocytes, subsequent affinity purification of modified GST-RhoA, and mass spectrometry identified attachment of putrescine or spermidine at glutamine-63 of RhoA. A comparison of putrescine, spermidine, and lysine as substrates for DNT-induced transglutamination of RhoA revealed that lysine is a preferred second substrate at least in vitro.

Animals↗
PubMed2001

Intravenous coronary angiography using synchrotron radiation: technical description and preliminary results.

BACKGROUND: Standard coronary angiography requires an arterial access and catheters; intravenous coronary angiography may image coronary arteries noninvasively and without catheters. The aim of this study was the assessment of the diagnostic accuracy of intravenous coronary angiography validated by selective coronary angiography. METHODS: Seventy outpatients (80% males, mean age 62 +/- 8 years) underwent both standard and intravenous coronary angiography after a previous coronary intervention. Intravenous coronary angiography was performed within 6 weeks before or after selective coronary angiography. Two different projections were used to obtain 6-8 sequences per patient. Images were taken after injection of the contrast agent into the brachial vein or into the superior vena cava. During image acquisition, patients were moved through the scanning beam on a special chair. Thereafter, images were evaluated and compared to selective coronary angiograms for the following criteria: no stenosis, subsignificant stenosis (< 70%), significant stenosis (> or = 70%), and occlusion. RESULTS: One hundred eighty-seven target vessels were analyzed. In 50 target vessels one or more stents had been implanted. Seventeen target vessels were not analyzable due to inadequate image quality. The sensitivity of intravenous coronary angiography for the detection of lesions was 80% and the specificity was 95%. The sensitivity for the detection of significant lesions in the left anterior descending coronary artery was 84% (specificity 93%), in the left circumflex coronary artery 67% (specificity 90%), in the right coronary artery 85% (specificity 97%), and in bypass grafts 85% (specificity 97%). No complications were observed. CONCLUSIONS: Intravenous coronary angiography is efficacious and safe and allows quantification of lesions of the coronary arteries and of bypass vessels. Further advances in image processing are needed to improve sensitivity especially in the left circumflex coronary artery.

Contrast Media↗
PubMed2000

Charge order in NaV2O5 studied by EPR

We present angular dependent EPR measurements in NaV2O5 at X-band frequencies in the temperature range 4.2</=T</=670 K. A detailed analysis in terms of the antisymmetric Dzyaloshinski-Moriya and the anisotropic exchange interactions yields the following scheme of charge order: On decreasing temperature a quarter-filled ladder with strong charge disproportions, existing for T>/=100 K, is followed by zigzag charge-order fluctuations which become long range and static below T(SP) = 34 K.

Journal Article↗
PubMed2000

Dendritic cells lose ability to present protein antigen after stimulating antigen-specific T cell responses, despite upregulation of MHC class II expression.

Immature dendritic cells (DC) take up, process and present protein antigens; mature DC are specialized for stimulating primary T cell responses with increased expression of MHC class II and co-stimulatory molecules, but are incapable of processing and presenting soluble protein. The current study examined whether maturation of DC is triggered by T cell recognition of antigens presented by immature DC. Human DC derived from CD34+ progenitor cells by culture with granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-6 (IL-6) in serum-free medium could prime naive CD4+ T cells to keyhole limpet hemocyanin (KLH) and ovalbumin (OVA). The cultured DC retained the ability to prime T cells to native protein for at least 15 days. To test for changes in DC function after participation in an immune response, DC were co-cultured with either allogeneic or autologous CD4+ T cells. DC co-cultured with autologous T cells retained the ability to prime T cells to intact protein antigens. By contrast, DC which had previously stimulated an allogeneic T cell response lost ability to prime T cells to soluble proteins. However, such < > induced a MLR and stimulated peptide-specific primary CD4+ T cell responses. This indicated that < > did not die or lose the ability to prime, but lost the ability to process and present subsequent antigens. Following participation in T cell activation, DC increased surface expression of MHC class II, co-stimulatory molecules CD40 and B7.2, and the intercellular adhesion molecule-1 (ICAM-1). In addition, our data suggest that interferon gamma (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha) are involved in this T cell-mediated DC maturation.

Antigen Presentation↗
PubMed2000

The gp130-stimulating designer cytokine hyper-IL-6 promotes the expansion of human hematopoietic progenitor cells capable to differentiate into functional dendritic cells.

OBJECTIVE: Hyper-IL-6, a fusion protein of interleukin-6 and its specific receptor, together with stem cell factor leads to the proliferation of primitive hematopoietic progenitor cells. Based on these findings, the current study examined whether hyper-IL-6 promotes the growth of precursor cells that can be further differentiated into dendritic cells in the presence of additional cytokines. METHODS: Dendritic cell cultures were generated from CD34(+) hematopoietic progenitor cells derived either from bone marrow or from peripheral blood. CD34(+) cells were cultured in the presence of cytokines for 2 weeks and then used for phenotyping and T-cell stimulation assays. RESULTS: Hyper-IL-6 in the presence of stem cell factor induced a 60- to 80-fold expansion of CD34(+) progenitor cells following 2 weeks of culture in serum-free medium. The addition of granulocyte-macrophage colony-stimulating factor to hyper-IL-6 and stem cell factor was essential for the differentiation of expanded progenitor cells into antigen presenting cells capable of inducing a primary T-cell response to soluble protein, which is a typical feature of dendritic cells. Phenotypic analyses confirmed the expansion of immature dendritic cells, which could be further differentiated into mature CD83(+) dendritic cells under the influence of interleukin-4, interleukin-1beta, tumor necrosis factor-alpha, and prostaglandin E(2). The capacity of expanded dendritic cells to stimulate protein-specific CD4(+) T cells was used to stimulate a primary T-helper cell response to the recombinant protein of the hepatitis-B core antigen in healthy donors. CONCLUSION: The expansion and differentiation of functional dendritic cells from CD34(+) progenitor cells under serum-free culture conditions allow for the possibility to develop more effective ways to immunize against viral infections and tumor diseases.

Antigen Presentation↗
PubMed2000

[Multiple primary carcinomas in patients with head and neck malignancies].

BACKGROUND: Multiple primary tumors can lead to diagnostic and therapeutical problems. In this study we surveyed frequency, localisation, diagnostic, chronologic and therapeutic aspects of multiple primary carcinomas in patients with head and neck tumors. PATIENTS AND METHODS: The data of 843 patients from the tumor registry of the ENT-clinic Aachen were retrospectively studied. RESULTS: Larynx (41.87%) and oropharynx (12.57%) were the main localisation of the first primary neoplasma. In 65 patients (7.71%) multiple primary tumors were observed. 24.6% of these tumors occurred synchronously. Preferential localisation of a second tumor were lung (20%), oral cavity (15.3%) and larynx (13.8%). 28.57% of the metachronous tumors were observed after more than five years. In 46.15% clinical complaints led to the suspicion of a second tumor. Panendoscopy was the most reliable diagnostic procedure. The survival rate and time was significantly reduced in patients with synchronous tumors. 3-year survival rate was 15% compared to 81% in patients with metachronous tumor appearance (p < 0.0001). CONCLUSION: Patients with head and neck tumors have a high incidence of multiple primary malignomas varying from the region of the first presentation of a malignant tumor. Concepts comprising surgery provide the highest survival rates. Because of the high incidence of metachronous carcinomas after five years found in this study, the authors regard a prolonged follow-up period as necessary.

Combined Modality Therapy↗
PubMed1998

Regulation of the subunit composition of plastidic glutamine synthetase of the wild-type and of the phytochrome-deficient aurea mutant of tomato by blue/UV-A- or by UV-B-light.

The photomorphogenetic aurea mutant of tomato severely deficient in spectrophotometrically active phytochromes was used to study the light-regulation of the single-copy nuclear gene encoding plastidic glutamine synthetase (GS-2; EC 6.1.3.2). The de-etiolation of dark-grown aurea mutant seedling cotyledons showed an obligatory dependency on blue light. A limited red light-responsiveness of etiolated aurea cotyledons is, however, retained as seen by the stimulation of both the GS-2 transcript and protein level in the cotyledons of aurea seedlings during growth in red light. The subunits of the octameric GS-2 enzyme were represented by polypeptides with similar electrophoretic mobilities (polypeptides a) in etiolated wild-type or aurea mutant cotyledons. GS-2 proteins with similar apparent molecular masses were also seen in the cotyledons of red light-grown aurea mutant seedlings. In contrast, GS-2 polypeptides with different apparent molecular masses (polypeptides a and b) were detected in the cotyledons of wild-type seedlings grown in red light. This difference indicates that the (post-translational) modification of tomato GS-2 subunit composition is mediated by the photoreceptor phytochrome. The illumination of etiolated wild-type or aurea cotyledons with UV-A- or UV-B-light light resulted in an increase in both the GS-2 transcript and protein level. Following illumination of etiolated wild-type seedlings with UV-A-light, the relative proportion of the GS-2 polypeptides a and b was similar than upon irradiation with blue light but different than after exposure to UV-B- or red light. This result suggests the involvement of a blue/ UV-A-light-specific photoreceptor in the regulation of tomato GS-2 subunit composition.

Gene Expression↗
PubMed1996

[Accidents caused by inflatable bouncers in 0-19 year-olds in Denmark in 1993].

The paper describes the epidemiology of accidents caused by inflatable bouncers. The estimated number of bouncers and bouncing castles in DK was 300-350 in 1993. The data were extracted from the Danish part of the EHLASS project ("the European Home and Leisure Accident Surveillance System). The project registers injuries in five Danish casualty wards, covering a total uptake area of 14.2% of the Danish population. In 1993, there were 91 injuries caused by inflatable bouncers, 37% of them in boys, and 63% in girls. Seventy-nine percent of the injuries were caused by falling, 19% by contact with an object or another person and 2% stress injuries. The type of injury were: bruises 42%, fractures 31%, distorsions 23%, and tendon/muscle strains 3%. The location of the fractures were: one in the spine, two in the clavicle, all other (25) were located in the limbs. Four patients had to be admitted for further observation or treatment. The average cost per injury was 839 dKr., or aprox 150 US$. It does not seem necessary to take special precautions or make restrictions in the use of this new playground article.

Accidents, Home↗
PubMed1996

Intravenous coronary angiography with dichromography using synchrotron radiation.

Dichromography represents a digital subtraction angiography mode based on energy substraction which allows imaging of fast moving subjects like the heart. For logarithmic subtraction 2 images with X-rays just below and above the iodine K-edge (33.17 keV) are simultaneously obtained in a line scan mode. Monochromatic X-rays of sufficient intensity to visualize coronary arteries of 1 mm diameter with extremely low iodine concentrations (1 mg/cm2) after venous injection is only provided by synchrotron radiation. The system NIKOS (non-invasive coronary arteriography with synchrotron radiation) at the Deutsches Elektronen Synchrotron (DESY) consists of 6 components: a wiggler, a monochromator, a safety system, a scanning device, a detector and a computer system. After experimental studies in dogs patients are imaged since 1990. Initial results demonstrate feasibility and safety of synchrotron radiation coronary angiography. Large scale studies are designed to further evaluate sensitivity and specificity. When compact synchrotron radiation sources become available, this technique could be used for follow-up studies and for evaluation of certain high coronary risk populations.

Angiography, Digital Subtraction↗
PubMed1995

[Eye injuries during hobby-work using machine tools].

Data from the EU-project EHLASS (European Home and Leisure Accident Surveillance System) collected from five Danish hospitals during the period 1989-1991 contained 185,551 accidents occurring at home and during leisure time. The population in the catchment area is approximately 700,000. Of these accidents, 9900 involved eye-injury, 2940 of these occurred during hobby-activities, and 1460 of these while the subject was using either drilling-, welding- or grinding-equipment. The incidence of eye-injuries occurring during the use of these machines has risen from 0.6/1000/year in 1989 to 0.7/1000/year in 1990 and to 0.8/1000/year in 1991. In 98% of the cases the patients were men, 30% were between 20 and 29 years of age. A common activity at the time of the accident was "car-repairing". Foreign-body-lesions were seen in 60% of the cases, and actinic conjunctivitis in 30%. None of the injuries were serious, but they were often very painful and demanding of resources. All the injuries could have been avoided by the use of proper eye protection.

Accidents, Home↗
PubMed1995

[Hand and wrist injuries. A study of 50.272 injuries].

This study reports the causes, characteristics and treatment of injuries to the hand and wrist presented to five accident and emergency departments in a two-year survey of 13% of the Danish population. The rate of injury to the hand or wrist was 28.6% of all injuries, or 3545 per 100,000 inhabitants per year. Thirty-four percent of the accidents were domestic, 35% were leisure accidents, 26% were occupational and 5% were traffic accidents. Only 2% of the patients were admitted to hospital for further treatment or observation and 13% were referred to a hospital as out-patients. The most frequent causes for admission were fractures (42%), tendon lesions (29%) and wounds (12%).

Accidents↗