PubMed Health⌕ Search

Biomedical subjects

D Baumann

Publications and source records attributed to D Baumann.

At least 19 recordsLinked to original sources
PubMed2003

[Fever after a tick bite: clinical manifestations and diagnosis of acute tick bite-associated infections in northeastern Switzerland].

BACKGROUND: Different tick-borne infections can cause an acute febrile illness. The study objectives were to investigate the clinical manifestations and diagnosis of infections among patients who presented with fever after a tick-bite, and to detect newly described pathogens, including Ehrlichia, Babesia and Rickettsia helvetica, in North-Eastern Switzerland. PATIENTS AND METHODS: : We studied 75 patients (41 male, 34 female, median age 38 years, among them 10 children) who had fever within 3 weeks after a tick-bite. Paired sera were tested for antibodies to Borrelia burgdorferi, tick-borne encephalitis virus, Anaplasma (Ehrlichia) phagocytophila, Babesia microti, B. divergens, and Rickettsia helvetica. In addition, microscopy and polymerase chain reaction was used to detect Ehrlichia. Clinical data were obtained at baseline and at 1 and 2 year follow-up. RESULTS: Tick-borne infections were confirmed or possible in 36 (48 %) patients: 7 (9 %) Erythema migrans, 6 (8 %) other specific manifestations of Lyme borreliosis, 6 (8 %) Lyme borreliosis presenting as non-specific febrile illness, 8 (11 %) tick-borne encephalitis, 7 (10 %) granulocytic ehrlichiosis, 1 B. microti infection in a traveler from the US and 6 (8 %) dual infections. In 8 (11 %) patients serological findings were suggesting possible acute or past R. helvetica infection. CONCLUSION: Among patients with fever after a tick-bite, Lyme borreliosis was most frequently found. There was no evidence for babesiosis among the resident population. Serologic data suggest that human granulocytic ehrlichiosis and R. helvetica infections may be endemic in Switzerland. Among 50 % of the patients no tick-borne infections could be diagnosed.

Acute Disease↗
PubMed2003

Macrophage labeling by SPIO as an early marker of allograft chronic rejection in a rat model of kidney transplantation.

Anatomical and functional information (renography, perfusion) was obtained by MRI in a life-supporting transplantation model, in which Lewis rats received kidneys from Fisher 344 donors. Renography and perfusion analyses were carried out with Gd-DOTA and small particles of iron oxide (SPIO), respectively. Starting 12 weeks posttransplantation, images from grafts of untreated recipients exhibited distinctive signal attenuation in the cortex. Animals treated with cyclosporin (Sandimmune Neoral; Novartis Pharma, Basel, Switzerland) to prevent acute rejection showed a signal attenuation in the cortex at 33 weeks posttransplantation, while kidneys from rats treated additionally with everolimus (Certican; Novartis), a rapamycin derivative, had no changes in anatomical appearance. A significant negative correlation was found between the MRI cortical signal intensity and the histologically determined iron content in macrophages located in the cortex. Renography revealed a significantly reduced functionality of the kidneys of untreated controls 33 weeks after transplantation, while no significant changes in perfusion were observed in any group of rats. These results suggest the feasibility, by labeling macrophages with SPIO, of detecting signs of graft rejection significantly earlier than when changes in function occur. Monitoring early changes associated with chronic rejection can have an impact in preclinical studies by shortening the duration of the experimental period and by facilitating the investigation of novel immunomodulatory therapies for transplantation.

Animals↗
PubMed2003

MRI-based monitoring of inflammation and tissue damage in acute and chronic relapsing EAE.

Experimental autoimmune encephalomyelitis (EAE) is a commonly used animal model that in several respects mimics human multiple sclerosis (MS), and can be used to design or validate new strategies for treatment of this disease. In the present study, different MRI techniques (macrophage tracking based on labeling cells in vivo by ultrasmall particles of iron oxide (USPIO), blood-brain barrier (BBB) breakdown, and magnetization transfer imaging (MTI)), as well as immunohistological staining were used to study the burden of disease in Lewis rats immunized by guinea pig myelin. The resulting imaging data was compared with behavioral readouts. Animals were studied during the acute phase and the first relapse. Activated monocytes were detected during both episodes in the brain stem or cortex. These areas coincided in part with areas of BBB breakdown. Significant changes of the magnetization transfer ratios (MTRs) of up to 35% were observed in areas of USPIO accumulation. This suggests that infiltrating monocytes are the major source of demyelination in EAE, but monocyte infiltration and breakdown of the BBB are temporally or spatially independent inflammatory processes.

Acute Disease↗
PubMed2003

Preparative purification of the major anti-inflammatory triterpenoid esters from Marigold (Calendula officinalis).

A method for the efficient preparative purification of faradiol 3-O-laurate, palmitate and myristate, the major anti-inflammatory triterpenoid esters in the flower heads of the medicinal plant Calendula officinalis has been developed. Gram quantities of the individual compounds were obtained with 96 to 98% purity by a combination of supercritical fluid extraction (SFE), normal-phase and reversed-phase column chromatography. During the work-up of the faradiol esters, accompanying minor compounds of the triterpene ester fraction were purified and identified by spectroscopic means as maniladiol 3-O-laurate and myristate.

Anti-Inflammatory Agents↗
PubMed2002

Measurement of the beam-helicity asymmetry in the p((-->)e,e'p)pi(0) reaction at the energy of the Delta(1232) resonance.

In a p((-->)e,e'p)pi(0) out-of-plane coincidence experiment at the three-spectrometer setup of the Mainz Microtron MAMI, the beam-helicity asymmetry has been precisely measured around the energy of the Delta(1232) resonance and Q(2) = 0.2(GeV/c)(2). The results are in disagreement with three up-to-date model calculations. This is interpreted as a lack of understanding of the nonresonant background, which in dynamical models is related to the pion cloud.

Journal Article↗
PubMed2002

In-vivo visualization of phagocytotic cells in rat brains after transient ischemia by USPIO.

Cerebral ischemia provokes tissue damage by two major patho-physiological mechanisms. Direct cell necrosis is induced by diminished access of neurons and glia to essential nutrients such as glucose and oxygen leading to energy failure. A second factor of cellular loss is related to the activation of immune-competent cells within and around the primary infarct. While granulocytes and presumably monocytes are linked to the no-reflow phenomenon, activated microglia cells and monocytes can release cytotoxic substrates, which cause delayed cell death. As a consequence the infarct volume will increase, despite restoration of cerebral perfusion. In the past, visualization of immune competent cells was only possible by histological analysis of post-mortem tissue. However, contrast agents based on small particles of iron oxide are known to accumulate in organs rich in cells with phagocytotic function. These particles can be tracked in vivo by MRI methods based on their relaxation properties. In the present study, the spatio-temporal distribution of USPIO particles was monitored in a rat model of transient cerebral infarction using T1- and T2-weighted MRI sequences. USPIO were detected in vessels at 24 h after administration. At later time points specific accumulation of USPIO was observed within the infarcted hemisphere, with maximal signal enhancement on day 2. Their detectability based on T1-contrast disappeared between day 4 and day 7. Immuno-histochemically (IHC) stains confirmed the presence of macrophages, presumably blood-derived monocytes within areas of T1 signal enhancement. Direct visualization of iron-burdened macrophages by IHC was only possible later than day 3 after occlusion.

Animals↗
PubMed2001

Neutral pion threshold production at Q(2) = 0.05 GeV(2)/c(2) and chiral perturbation theory.

New data are presented on the p(e,e'p)pi(0) reaction at threshold at a four-momentum transfer of Q(2) = 0.05 GeV(2)/c(2). The data were taken with the three-spectrometer setup of the A1 Collaboration at the Mainz Microtron MAMI. The complete center of mass solid angle was covered up to a center of mass energy of 4 MeV above threshold. Combined with measurements at three different values of the virtual photon polarization epsilon, the structure functions sigma(T), sigma(L), sigma(TT), and sigma(TL) are determined. The results are compared with calculations in heavy baryon chiral perturbation theory and with a phenomenological model. The measured cross section is significantly smaller than both predictions.

Journal Article↗
PubMed2001

A central role for the armadillo protein plakoglobin in the autoimmune disease pemphigus vulgaris.

In pemphigus vulgaris (PV), autoantibody binding to desmoglein (Dsg) 3 induces loss of intercellular adhesion in skin and mucous membranes. Two hypotheses are currently favored to explain the underlying molecular mechanisms: (a) disruption of adhesion through steric hindrance, and (b) interference of desmosomal cadherin-bound antibody with intracellular events, which we speculated to involve plakoglobin. To investigate the second hypothesis we established keratinocyte cultures from plakoglobin knockout (PG-/-) embryos and PG+/+ control mice. Although both cell types exhibited desmosomal cadherin-mediated adhesion during calcium-induced differentiation and bound PV immunoglobin (IgG) at their cell surface, only PG+/+ keratinocytes responded with keratin retraction and loss of adhesion. When full-length plakoglobin was reintroduced into PG-/- cells, responsiveness to PV IgG was restored. Moreover, in these cells like in PG+/+ keratinocytes, PV IgG binding severely affected the linear distribution of plakoglobin at the plasma membrane. Taken together, the establishment of an in vitro model using PG+/+ and PG-/- keratinocytes allowed us (a) to exclude the steric hindrance only hypothesis, and (b) to demonstrate for the first time that plakoglobin plays a central role in PV, a finding that will provide a novel direction for investigations of the molecular mechanisms leading to PV, and on the function of plakoglobin in differentiating keratinocytes.

Animals↗
PubMed2001

Measurement of the recoil polarization in the p(e-->, e'p-->)pi(0) reaction at the Delta(1232) resonance.

The recoil proton polarization has been measured in the p(e-->,e'p-->)pi(0) reaction in parallel kinematics around W = 1232 MeV, Q2 = 0.121 (GeV/c)2, and epsilon = 0.718 using the polarized cw electron beam of the Mainz Microtron. All three proton polarization components, Px/P(e) = (-11.4+/-1.3+/-1.4)%, P(y) = (-43.1+/-1.3+/-2.2)%, and P(z)/P(e) = (56.2+/-1.5+/-2.6)%, could be measured simultaneously. The Coulomb quadrupole to magnetic dipole ratio, CMR = (-6.4+/-0.7(stat)+/-0.8(syst))%, was determined from Px in the framework of the Mainz Unitary Isobar Model. The consistency among the reduced polarizations and the extraction of the ratio of longitudinal-to-transverse response is discussed.

Journal Article↗
PubMed2001

Bicuculline-induced brain activation in mice detected by functional magnetic resonance imaging.

Dynamic measurements of local changes in relative cerebral blood volume (CBV(rel)) during a pharmacological stimulation paradigm were performed in mice. Using magnetite nanoparticles as an intravascular contrast agent, high-resolution CBV(rel) maps were obtained. Intravenous administration of the GABA(A) antagonist bicuculline prompted increases in local CBV(rel) as assessed by MRI with a high spatial resolution of 0.2 x 0.2 mm(2) and a temporal resolution of 21 s. Signal changes occurred 20-30 s after the onset of drug infusion in the somatosensory and motor cortex, followed by other cortical and subcortical structures. The magnitudes of the CBV(rel) increases were 18% +/- 4%, 46% +/- 14%, and 67% +/- 7%, as compared to prestimulation values for the cortex, and 9% +/- 3%, 25% +/- 4%, and 36% +/- 7% for the caudate putamen for bicuculline doses of 0.6, 1.25, and 1.5 mg/kg, respectively. On-line monitoring of transcutaneous carbon dioxide tension PtcCO(2) reflecting arterial PaCO(2) did not show any alteration during the stimulation paradigm. One of five of the mice receiving the highest bicuculline dose, and three of seven receiving the intermediate dose displayed a different cortical response pattern. After a CBV(rel) increase of 40% lasting for approximately 1 min, significant CBV(rel)reductions by 80% have been observed. Subcortical structures did not display this behavior. The present study suggests that this noninvasive approach of functional MRI (fMRI) can be applied to study drug-induced brain activation by central nervous system (CNS) drugs in mice under normal and pathological situations.

Animals↗
PubMed2001

Current awareness.

In order to keep subscribers up-to-date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of NMR in biomedicine. Each bibliography is divided into 9 sections: 1 Books, Reviews ' Symposia; 2 General; 3 Technology; 4 Brain and Nerves; 5 Neuropathology; 6 Cancer; 7 Cardiac, Vascular and Respiratory Systems; 8 Liver, Kidney and Other Organs; 9 Muscle and Orthopaedic. Within each section, articles are listed in alphabetical order with respect to author. If, in the preceding period, no publications are located relevant to any one of these headings, that section will be omitted.

Magnetic Resonance Spectroscopy↗
PubMed2001

Non-invasive, quantitative assessment of the anatomical phenotype of corticotropin-releasing factor-overexpressing mice by MRI.

High resolution magnetic resonance imaging (MRI) was applied to quantify alterations in thymus and adrenal volumes, as well as body fat in genetically engineered corticotropin-releasing factor (CRF)-overexpressing mice. When compared to the organs in age-matched wild-type animals, the adrenals in CRF-overexpressing male mice were significantly enlarged and the thymus volume in females was significantly smaller. The fat content was significantly larger in CRF-overexpressing mice. The anatomical alterations observed in the MRI studies were in perfect line with post-mortem data (weights of organs). Furthermore, the observed interstrain differences are in agreement with recently published data on (i) the effect of continuous, intraventricular infusion of CRF in rats and (ii) the presence of atrophic adrenals in CRF-knockout mice. The present studies demonstrate that MRI can provide reliable measures of relatively small structures such as the adrenal glands and the thymus in mice. This makes MRI an attractive, non-terminal tool to monitor in laboratory animals, including transgenic mice, the consequence of continuous stress on relevant organs.

Adipose Tissue↗
PubMed2001

MRI analysis of the changes in apparent water diffusion coefficient, T(2) relaxation time, and cerebral blood flow and volume in the temporal evolution of cerebral infarction following permanent middle cerebral artery occlusion in rats.

Detailed knowledge of similarities and differences between animal models and human stroke is decisive for selecting clinically effective drugs based on efficacy data obtained preclinically. Differences in the temporal evolution of stroke pathologies between animal models and man have been reported. In view of the importance of this issue for the development of neuroprotective treatments, the temporal evolution of stroke pathologies in the rat permanent middle cerebral artery occlusion (pMCAO) model has been evaluated with magnetic resonance imaging modalities under experimental conditions matching as close as possible those used in humans. Changes in the ipsilateral and contralateral cortex and striatum of cerebral blood flow (CBF) and volume (CBV), apparent diffusion coefficient (ADC), and spin-spin relaxation time (T(2)), as well as total cortical and striatal infarct volumes, calculated from CBF, ADC, and T(2) maps, were determined starting 1 h up to 216 h post-pMCAO. The temporal evolution of the MRI parameters in this rat model was similar to that observed in humans. In particular, the ADC values were decreased for more than 3 days and returned back to baseline between 4 to 8 days, to increase by day 9 only. Thus the stroke pathology in this rat model develops at a similar pace as in stroke patients arguing against a fundamental difference in the mechanisms involved. The infarct volumes however develop differently in this rat model as they invariably increase over the first 48 h, while in humans the evolution of infarct volume is slower and more heterogeneous.

Animals↗
PubMed2001

Comparison of analgesic techniques for antler removal in wapiti.

The purpose of this research was to compare the effectiveness of ring block anesthesia (LA) and electroanesthesia (A) for antler removal in elk given a long-acting tranquilizer to remove stress from restraint. Thirty-two male wapiti were given 1 mg/kg body weight of zuclopenthixol acetate; the next day, they were restrained in a hydraulic chute, provided with electroanesthesia or a lidocaine ring block, and had their antlers removed. Behavioral response to antler removal was scored. Significantly more (P = 0.032) animals responded to antler removal in the EA group. Heart rates and arterial pressures were measured by a catheter connected to a physiological monitor. Heart rate increased significantly over time with EA, but not with LA. Heart rate increased from baseline significantly more in the EA group immediately prior to antler removal (P = 0.017), immediately post antler removal (P = 0.001), and at 1 min post antler removal (P = 0.037). It was concluded that EA is not as effective a method of anesthesia as is LA for antler removal.

Animals↗
PubMed2000

[Serologic and clinical evidence for endemic occurrences of human granulocytic ehrlichiosis in North-Eastern Switzerland].

BACKGROUND: Tick-borne human granulocytic ehrlichiosis (HGE) has not been diagnosed in Switzerland, although the HGE agent has been identified in ticks and animal reservoirs and human infections have been suspected on the basis of serological surveys. METHODS: We retrospectively tested sera of 48 persons with antibodies to B. burgdorferi and/or tick-borne encephalitis virus for the presence of antibodies to E. phagocytophila (a surrogate marker of the agent of HGE), and reviewed their charts with regard to clinical manifestations possibly associated with a tick-borne infection. We then prospectively examined EDTA blood of 80 patients who presented with fever 7 to 21 days after a tick bite for the presence of the HGE agent (using nested PCR and microscopic examination of blood smears) and anti-E. phagocytophila antibodies. We also collected clinical data. RESULTS: The retrospective study revealed 12 persons (25%) with anti-E. phagocytophila antibody titers > or = 1:80, suggesting coinfection with HGE and either Lyme Borrelia or tick-borne encephalitis virus. Among these, 7 patients presented with clinical manifestations compatible with HGE disease. The prospective investigation identified 8 patients (10%) with anti-E. phagocytophila antibody titers > or = 1:80, and 7 of these presented with signs and symptoms suggesting HGE. The HGE agent, however, was detected neither by PCR nor by microscopic examination. CONCLUSIONS: Serological and clinical data suggest the occurrence of an HGE-like agent as well as of coinfections with HGE and B. burgdorferi or tick-borne encephalitis virus in Switzerland. However, the HGE agent was not identified in persons living in Switzerland.

Adolescent↗
PubMed2000

First determination of generalized polarizabilities of the proton by a virtual compton scattering experiment

Absolute differential cross sections for the reaction ep-->epgamma have been measured at a four-momentum transfer with virtuality Q2 = 0.33 GeV2 and polarization epsilon = 0.62 in the range 33.6 to 111.5 MeV/c for the momentum of the outgoing photon in the photon-proton center of mass frame. The experiment has been performed with the high-resolution spectrometers at the Mainz Microtron MAMI. From the photon angular distributions, two structure functions which are a linear combination of the generalized polarizabilities have been determined for the first time.

Journal Article↗
PubMed2000

Regional brain activation by bicuculline visualized by functional magnetic resonance imaging. Time-resolved assessment of bicuculline-induced changes in local cerebral blood volume using an intravascular contrast agent.

Functional magnetic resonance imaging (fMRI) has been applied to study rat focal brain activation induced by intravenous administration of the GABA(A) antagonist bicuculline. Using magnetite nanoparticles as a blood pool contrast agent, local changes in cerebral blood volume (CBV) were assessed with high temporal (10 s) and spatial (0.35 x 0.6 mm(2)) resolutions. Upon infusion of the bicuculline region-specific increases in CBV have been observed, suggesting CBV to reflect brain activity. During the first 2 min, the signal increases were predominant in the cortex, followed by increases in other brain areas, such as the caudate putamen, thalamus and cerebellum. Ten minutes after the start of infusion, a dominant response was observed in the thalamus, while in the caudate putamen a biphasic response pattern was seen. The magnitude of the signal responses in all brain regions was dependent on the dose of bicuculline and, in general, matched the known distribution of GABA(A) binding sites. This study suggests that pharmacological fMRI, displaying brain function at the highly specific level of drug-receptor interaction, should foster our understanding of normal and pathological brain function.

Animals↗