PubMed Health⌕ Search

Biomedical subjects

Bjarne Krebs

Publications and source records attributed to Bjarne Krebs.

12 recordsLinked to original sources
PubMed2007

Brain protein preservation largely depends on the postmortem storage temperature: implications for study of proteins in human neurologic diseases and management of brain banks: a BrainNet Europe Study.

The present study was designed to reveal protein modifications in control cases related with postmortem delay and temperature of storage in 3 paradigms in which the same postmortem tissue sample (frontal cortex) was frozen a short time after death or stored at 1 degrees C, 4 degrees C, or room temperature and then frozen at -80 degrees C at different intervals. No evidence of protein degradation as revealed with monodimensional gel electrophoresis and Western blotting was observed in samples artificially stored at 1 degrees C and then frozen at different intervals up to 50 hours after death. However, the levels of several proteins were modified in samples stored at 4 degrees C and this effect was more marked in samples stored at room temperature. Two-dimensional gel electrophoresis and mass spectrometry further corroborated these observations and permitted the identification of other proteins vulnerable or resistant to postmortem delay. Finally, gel electrophoresis and Western blotting of sarkosyl-insoluble fractions in Alzheimer disease showed reduced intensity of phospho-tau-specific bands with postmortem delay with the effects being more dramatic when the brain samples were stored at room temperature for long periods. These results emphasize the necessity of reducing the body temperature after death to minimize protein degradation.

Aged↗
PubMed2006

Synapse formation and function is modulated by the amyloid precursor protein.

The amyloid precursor protein (APP) is critical in the pathogenesis of Alzheimer's disease. The question of its normal biological function in neurons, in which it is predominantly located at synapses, is still unclear. Using autaptic cultures of hippocampal neurons, we demonstrate that hippocampal neurons lacking APP show significantly enhanced amplitudes of evoked AMPA- and NMDA-receptor-mediated EPSCs. The size of the readily releasable synaptic vesicle pool was also increased in neurons lacking APP, whereas the release probability was not affected. In addition, the analysis of spontaneous miniature synaptic currents revealed an augmented frequency in neurons lacking APP, whereas the amplitude of miniature synaptic currents was not found to be altered. Together, these findings strongly indicate that lack of APP increases the number of functional synapses. This hypothesis is further supported by morphometric immunohistochemical analysis revealing an increase of synaptophysin-positive puncta per cultured APP knock-out neuron. In conclusion, lack of APP affects synapse formation and transmission in cultured hippocampal neurons.

Action Potentials↗
PubMed2006

A method to perform Western blots of microscopic areas of histological sections.

Western blotting is one powerful research method to specifically detect proteins. However, it has been barely possible to investigate microscopic volumes of tissue so far because of the required minimum volumes and the pretreatment. Herein, we describe a method of performing Western blots directly from the histological section of frozen or paraffin-embedded tissue. Small histological areas of a mouse brain were lysed by section lysis buffer, subjected to a miniaturized SDS-PAGE, and detected by immunoblotting. Thereby, an area equivalent to only 15 cortical neurons of mouse cortex was detectable. This offers the possibility of correlating histological findings to biochemical investigations. In addition, enzymatic pretreatment was applied to identify the glycosylation of the major cleavage product of the prion protein. Moreover, the section lysis buffer is a sophisticated method to conserve and investigate phosphorylation sites as demonstrated here by phopsphorylated Akt and ERK. The presented technique combines histology with Western blotting techniques and will be of value for investigations of discrete tissue areas.

Animals↗
PubMed2006

Dose-related influence of sodium selenite on apoptosis in human thyroid follicles in vitro induced by iodine, EGF, TGF-beta, and H2O2.

Apoptosis of thyroid follicular cells is induced by high doses of iodide, epidermal growth factor (EGF), transforming growth factor-beta (TGF-beta), as well as H2O2 and might be attenuated by antioxidants. Therefore, we examined the apoptotic index induced by these substances in selenium-treated vs untreated human thyroid follicular cells. Reconstituted human thyroid follicles were incubated with sodium selenite (10 or 100 nM) for 72 h; controls received none. The follicles were then distributed to 24-well plates and incubated with potassium iodide (5, 10, or 20 nM), EGF (5 ng/mL), TGF-beta (5 ng/mL), or H2O2 (100 muM). Apoptosis was determined by a mitochondrial potential assay and the number of apoptotic cells counted by two independent, experienced technicians and the glutathione peroxidase (GPx) activity was determined. Asignificant increase of apoptic cells was obtained in control thyroid follicles treated with iodine (5, 10, or 20 microM), thyroidstimulating hormone (TSH) 1, or 10 mU/mL in combination with 5 and 10 microM iodine, EGF (5 ng/mL) and TGF-beta (5 ng/mL), or H2O2 (100 microM) (p < 0.001). In contrast, in thyroid follicles preincubated with 10 or 100 nM sodium selenite, the apoptototic index was identical to the basal rate. In H2O2-treated follicles, the apoptotic index was still significantly elevated but 50% lower compared to control cells. The GPx activity increased from 1.4 +/- 0.2 to 2.25 +/- 0.4 mU/microg DNA with 10 nMselenite and 2.6 + 0.4 mU/microg DNA with 100 nM selenite. Sodium selenite might increase the antioxidative potential in human thyroid follicles in vitro and therefore diminish the apoptosis induced by TGF-beta, EGF, iodide, and even H2O2.

Apoptosis↗
PubMed2005

Prion protein induced signaling cascades in monocytes.

Prion proteins play a central role in transmission and pathogenesis of transmissible spongiform encephalopathies. The cellular prion protein (PrP(C)), whose physiological function remains elusive, is anchored to the surface of a variety of cell types including neurons and cells of the lymphoreticular system. In this study, we investigated the response of a mouse monocyte/macrophage cell line to exposure with PrP(C) fusion proteins synthesized with a human Fc-tag. PrP(C) fusion proteins showed an attachment to the surface of monocyte/macrophages in nanomolar concentrations. This was accompanied by an increase of cellular tyrosine phosphorylation as a result of activated signaling pathways. Detailed investigations exhibited activation of downstream pathways through a stimulation with PrP fusion proteins, which include phosphorylation of ERK(1,2) and Akt kinase. Macrophages opsonize and present antigenic structures, contact lymphocytes, and deliver cytokines. The findings reported here may become the basis of understanding the molecular function of PrP(C) in monocytes and macrophages.

Animals↗
PubMed2005

Activation of phosphatidylinositol 3-kinase by cellular prion protein and its role in cell survival.

The cellular prion protein (PrP(C)) is thought to be involved in protection against cell death, however the exact cellular mechanisms involved are still controversial. Herein we present data that strongly indicate a functional link between PrP(C) expression and phosphatidylinositol 3-kinase (PI 3-kinase) activation, a protein kinase that plays a pivotal role in cell survival. Both mouse neuroblastoma N2a cells and immortalized murine hippocampal neuronal cell lines expressing wild-type PrP(C) had significantly higher PI 3-kinase activity levels than their respective controls. Moreover, PI 3-kinase activity was found to be elevated in brain lysates from wild-type mice, as compared to prion protein-knockout mice. Recruitment of PI 3-kinase by PrP(C) was shown to contribute to cellular survival toward oxidative stress by using 3-morpholinosydnonimine (SIN-1) and serum deprivation. Moreover, both PI 3-kinase activation and cytoprotection by PrP(C) appeared to rely on copper binding to the N-terminal octapeptide of PrP(C). Thus, we propose a model in which the interaction of copper(II) with the N-terminal domain of PrP(C) enables transduction of a signal to PI 3-kinase; the latter, in turn, mediates downstream regulation of cell survival.

Animals↗
PubMed2005

Creutzfeldt-Jakob disease in a patient with an R208H mutation of the prion protein gene (PRNP) and a 17-kDa prion protein fragment.

A case of Creutzfeldt-Jakob disease (CJD) with a rare mutation of the prion protein (PrP) gene (PRNP) at codon 208 (R208H) is described. By comparison with two preceding reports, the case described here displayed two distinct biochemical and neuropathological features. Western blot analysis of brain homogenates showed, in addition to the commonly observed three bands of abnormal protease-resistant PrP isoform (PrP(Sc)), an additional band of about 17 kDa. Neuropathological examination of the post mortem brain revealed tau pathology in the hippocampus and entorhinal cortex, as well as ballooned neurons in the cortex, hippocampus and subcortical gray matter.

Aged↗
PubMed2004

Expression of matrix metalloproteinases and their inhibitors in medulloblastomas and their prognostic relevance.

PURPOSE AND EXPERIMENTAL DESIGN: The cellular mechanisms leading to metastatic disease in medulloblastoma (MB), the most common malignant brain tumor in childhood, are mainly unknown. Recently, however, the involvement of matrix metalloproteinases (MMPs) has been suggested. We examined the expression and localization of four MMPs-MMP-2 and -9, membrane-type 1 and 2 MMP (MT1- and MT2-MMP)-and correlated the data with those for their main inhibitors, tissue inhibitors of metalloproteinases (TIMP-1, -2, and -3), in 83 classical and 18 desmoplastic MBs. RESULTS: Independent of the histological subtype, MMP-2 expression was found in a small percentage of tumors, whereas MMP-9 and MT1- or MT2-MMP were expressed in >75% of tumor samples. The expression of TIMP-1, -2, and -3, on the other hand, was found to depend on the histological subtype: TIMP-3 was often found in classical MB, whereas TIMP-2 was often expressed in desmoplastic MB (P = 0.007-0.001). In addition, both TIMP-3 and -2 correlated significantly with the expression of all studied metalloproteinases except MMP-2. TIMP-1, detected only in classical MB in a low percentage, was the only TIMP that correlated with the expression of MMP-2. Kaplan-Meier estimation revealed significantly reduced long-term survival of patients with strong MMP expression in tumor samples. In multivariate logistic regression analysis, however, the prognosis was significantly determined only by clinical parameters. CONCLUSIONS: TIMP-3 and -2 expression is highly correlated with histological subtypes of MBs and strongly associated with the expression of certain MMPs. The expression of TIMPs and MMPs, however, does not determine prognosis independently of clinical parameters.

Adolescent↗
PubMed2003

Tolerability of malaria chemoprophylaxis in non-immune travellers to sub-Saharan Africa: multicentre, randomised, double blind, four arm study.

OBJECTIVE: To compare the tolerability of malaria chemoprophylaxis regimens in non-immune travellers. DESIGN: Randomised, double blind, study with placebo run-in phase. SETTING: Travel clinics in Switzerland, Germany, and Israel. MAIN OUTCOME MEASURE: Proportion of participants in each treatment arm with subjectively moderate or severe adverse events. PARTICIPANTS: 623 non-immune travellers to sub-Saharan Africa: 153 each received either doxycycline, mefloquine, or the fixed combination chloroquine and proguanil, and 164 received the fixed combination atovaquone and proguanil. RESULTS: A high proportion of patients reported adverse events, even in the initial placebo group. No events were serious. The chloroquine and proguanil arm had the highest proportion of mild to moderate adverse events (69/153; 45%, 95% confidence interval 37% to 53%), followed by mefloquine (64/153; 42%, 34% to 50%), doxycycline (51/153; 33%, 26% to 41%), and atovaquone and proguanil (53/164; 32%, 25% to 40%) (P = 0.048 for all). The mefloquine and combined chloroquine and proguanil arms had the highest proportion of more severe events (n = 19; 12%, 7% to 18% and n = 16; 11%, 6% to 15%, respectively), whereas the combined atovaquone and proguanil and doxycycline arms had the lowest (n = 11; 7%, 2% to 11% and n = 9; 6%, 2% to 10%, respectively: P = 0.137 for all). The mefloquine arm had the highest proportion of moderate to severe neuropsychological adverse events, particularly in women (n = 56; 37%, 29% to 44% versus chloroquine and proguanil, n = 46; 30%, 23% to 37%; doxycycline, n = 36; 24%, 17% to 30%; and atovaquone and proguanil, n = 32; 20%, 13% to 26%: P = 0.003 for all). The highest proportion of moderate or severe skin problems were reported in the chloroquine and proguanil arm (n = 12; 8%, 4% to 13% versus doxycycline, n = 5; 3%, 1% to 6%; atovaquone and proguanil, n = 4; 2%, 0% to 5%; mefloquine, n = 2; 1%, 0% to 3%: P = 0.013). CONCLUSIONS: Combined atovaquone and proguanil and doxycyline are well tolerated antimalarial drugs. Broader experience with both agents is needed to accumulate reports of rare adverse events.

Adolescent↗
PubMed2002

Selenium supplementation in patients with autoimmune thyroiditis decreases thyroid peroxidase antibodies concentrations.

In areas with severe selenium deficiency there is a higher incidence of thyroiditis due to a decreased activity of selenium-dependent glutathione peroxidase activity within thyroid cells. Selenium-dependent enzymes also have several modifying effects on the immune system. Therefore, even mild selenium deficiency may contribute to the development and maintenance of autoimmune thyroid diseases. We performed a blinded, placebo-controlled, prospective study in female patients (n = 70; mean age, 47.5 +/- 0.7 yr) with autoimmune thyroiditis and thyroid peroxidase antibodies (TPOAb) and/or Tg antibodies (TgAb) above 350 IU/ml. The primary end point of the study was the change in TPOAb concentrations. Secondary end points were changes in TgAb, TSH, and free thyroid hormone levels as well as ultrasound pattern of the thyroid and quality of life estimation. Patients were randomized into 2 age- and antibody (TPOAb)-matched groups; 36 patients received 200 microg (2.53 micromol) sodium selenite/d, orally, for 3 months, and 34 patients received placebo. All patients were substituted with L-T(4) to maintain TSH within the normal range. TPOAb, TgAb, TSH, and free thyroid hormones were determined by commercial assays. The echogenicity of the thyroid was monitored with high resolution ultrasound. The mean TPOAb concentration decreased significantly to 63.6% (P = 0.013) in the selenium group vs. 88% (P = 0.95) in the placebo group. A subgroup analysis of those patients with TPOAb greater than 1200 IU/ml revealed a mean 40% reduction in the selenium-treated patients compared with a 10% increase in TPOAb in the placebo group. TgAb concentrations were lower in the placebo group at the beginning of the study and significantly further decreased (P = 0.018), but were unchanged in the selenium group. Nine patients in the selenium-treated group had completely normalized antibody concentrations, in contrast to two patients in the placebo group (by chi(2) test, P = 0.01). Ultrasound of the thyroid showed normalized echogenicity in these patients. The mean TSH, free T(4), and free T(3) levels were unchanged in both groups. We conclude that selenium substitution may improve the inflammatory activity in patients with autoimmune thyroiditis, especially in those with high activity. Whether this effect is specific for autoimmune thyroiditis or may also be effective in other endocrine autoimmune diseases has yet to be investigated.

Adult↗
PubMedDate not supplied

A fatal encephalitis.

Explore the source record for details and available documents.

Encephalitis, Viral↗