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Biomedical subjects

P Jakob

Publications and source records attributed to P Jakob.

At least 19 recordsLinked to original sources
PubMed2006

Efficacy of amphoteric surfactant- and peracetic acid-based disinfectants on spores of bacillus cereus in vitro and on food premises of the German armed forces.

In mass catering facilities of the German Armed Forces, foodborne outbreaks are commonly attributed to Bacillus cereus, and spores of this organism are regularly found on equipment surfaces. B. cereus is the causative agent of foodborne emetic or diarrheic disease. Hence, the use of sporicidal disinfectants may provide a starting point for successful risk mitigation of diseases associated with B. cereus. In this study, the amphoteric surfactant-based disinfectant (product A) that has been routinely used in catering facilities of the German Armed Forces and a peracetic acid-based disinfectant (product B) were compared for their efficacy against B. cereus spores in laboratory tests and under field conditions. In a carrier test for B. cereus spores, product A displayed no efficacy against spores of the test strain. In contrast, a substantial reduction in spore concentration (>5-log reduction) was achieved with product B. In a controlled trial conducted in seven Army catering facilities, the reduction in the number of B. cereus-positive samples was significantly greater (P < 0.001) for product B (from 28% initial contamination to 3% after application) than for product A (from 33 to 21%). Product B was estimated to be 6.25 times more efficacious than product A. Field trials confirmed the higher efficacy of the peracetic acid-based disinfectant to reduce B. cereus contamination on surfaces as found for the in vitro experiments. The tests used to assess the sporicidal effects of disinfectants were adequate under practice conditions and could be used for sporicidal testing of disinfectants for catering and food production establishments.

Bacillus cereus↗
PubMed2006

In vivo high-resolution MR imaging of neuropathologic changes in the injured rat spinal cord.

BACKGROUND AND PURPOSE: MR imaging is the most comprehensive noninvasive means to assess structural changes in injured central nervous system (CNS) tissue in humans over time. The few published in vivo MR imaging studies of spinal cord injury in rodent models by using field strengths < or = 7T suffer from low spatial resolution, flow, and motion artifacts. The aim of this study was to assess the capacity of a 17.6T imaging system to detect pathologic changes occurring in a rat spinal cord contusion injury model ex vivo and in vivo. METHODS: Seven adult female Fischer 344 rats received contusion injuries at thoracic level T10, which caused severe and reproducible lesions of the injured spinal cord parenchyma. Two to 58 days postinjury, high-resolution MR imaging was performed ex vivo (2) or in vivo in anesthetized rats (5 spinal cord injured + one intact control animal) by using 2D multisection spin- and gradient-echo imaging sequences, respectively, combined with electrocardiogram triggering and respiratory gating. RESULTS: The acquired images provided excellent resolution and gray/white matter differentiation without significant artifacts. Signal intensity changes, which were detected with ex vivo and in vivo MR imaging following spinal cord injury, could be correlated with histologically defined structural changes such as edema, fibroglial scar, and hemorrhage. CONCLUSIONS: These results demonstrate that MR imaging at 17.6T allows high-resolution structural analysis of spinal cord pathology after injury.

Animals↗
PubMed2004

Depletion of the high-abundance plasma proteins.

Body fluids, like plasma and urine, are comparatively easy to obtain and are useful for the detection of novel diagnostic markers by applying new technologies, like proteomics. However, in plasma, several high-abundance proteins are dominant and repress the signals of the lower-abundance proteins, which then become undetectable either by two-dimensional gels or chromatography. Therefore, depletion of the abundant proteins is a prerequisite for the detection of the low-abundance components. We applied affinity chromatography on blue matrix and Protein G and removed the most abundant human plasma proteins, albumin and the immunoglobulin chains. The plasma proteins, prior to albumin and immunoglobulin depletion, as well the eluates from the two chromatography steps were analyzed by two-dimensional electrophoresis and the proteins were identified by MALDI-TOF-MS. The analysis resulted in the identification of 83 different gene products in the untreated plasma. Removal of the high-abundance proteins resulted in the visualization of new protein signals. In the eluate of the two affinity steps, mostly albumin and immunoglobulin spots were detected but also spots representing several other abundant plasma proteins. The methodology is easy to perform and is useful as a first step in the detection of diagnostic markers in body fluids by applying proteomics technologies.

Blood Proteins↗
PubMed2004

High density gradients in the (square root 3 x square root 3)R30 degrees-CO layer on Ru(0001).

The coverage regime just beyond 0.33 ML, representative of a perfectly ordered (square root 3 x square root 3)R30 degrees-CO layer on Ru(0001), has been investigated using infrared-absorption spectroscopy. Different isotopic mixtures of CO have been employed to derive a profound understanding of structural properties of such layers. It is found that extra CO molecules incorporated into the (square root 3 x square root 3)R30 degrees-CO layer affect their nearest neighbor molecules only, and the associated density gradient extends over no more than a few angstroms. Contrary to existing belief, the model system CO on Ru(0001) does not represent a case of an unusually shallow adsorption potential corrugation. Rather, CO experiences an exceptionally strong site preference when adsorbed on Ru(0001). Annealing causes the local distortion of the overlattice to propagate laterally, most probably in a density wave-like manner. Incipient motion on the atomic scale thereby has been detected by means of isotopic labeling of inequivalent molecules within the high density areas. All major conclusions are based on observations of (isotopically labeled) minority CO species which feature negligible dynamical lateral coupling. The majority CO species, on the other hand, provide laterally averaged, unspecific information on the status of the layer.

Journal Article↗
PubMed2003

Surface strain versus substrate interaction in heteroepitaxial metal layers: Pt on Ru(0001).

By studying the adsorption of CO on up to 30 layers of Pt deposited on Ru(0001) the influence of surface strain on the adsorption energy has been disentangled from the residual chemical interaction with the substrate. While the electronic influence of the substrate has largely vanished for three Pt layers, the effect of surface strain due to the 2.5% lattice mismatch of Pt and Ru remains initially intact and is only gradually released for n>/=5 Pt layers. Electronic structure calculations confirm the experimental observations, in particular, the dramatic decrease of the CO adsorption energy on a single Pt layer which is caused by the strong Pt-Ru interlayer coupling.

Journal Article↗
PubMed2000

Hemosuccus pancreaticus--a rare cause of gastrointestinal bleeding: diagnosis and interventional radiological therapy.

Hemorrhage from the pancreatic duct, i.e. hemosuccus pancreaticus (HP), is a rare cause of gastrointestinal bleeding. Pancreatic hemosuccus is usually due to the rupture of an aneurysm of a visceral artery, most likely the splenic artery, in chronic pancreatitis. Other causes of HP are rare. We present a case of HP in a female patient with no history but with positive findings of chronic calcifying pancreatitis upon ultrasonographic investigation, computed tomography scan, and endoscopic retrograde cholangiopancreatography. With detectable fresh blood in the descending duodenum, angiography of the celiac artery revealed an aneurysm of the splenic artery as the suspected cause of intermittent bleeding from the pancreatic duct. The treatment is traditionally surgical or by interventional radiological means. This is the first case described in the literature in which interventional radiological therapy involved implantation of an uncoated metal Palmaz stent in the splenic artery. In the follow-up of 18 months no relapse of HP was observed.

Aneurysm, Ruptured↗
PubMed1998

Effect of substrate strain on adsorption

Direct evidence for the effect of local strain at a surface on the bonding strength for adsorbates is presented. Scanning tunneling microscopy revealed that adsorbed oxygen atoms on Ru(0001) surfaces are located preferentially on top of nanometer-size protrusions above subsurface argon bubbles, where tensile strain prevails, and are depleted around their rim in regions of compression, relative to the flat surface. Such effects can be considered as the reverse of adsorbate-induced strain, and their direct local demonstration can be used to test theoretical predictions.

Journal Article↗
PubMed1998

Crystal structure of fructose-1,6-bisphosphate aldolase from the human malaria parasite Plasmodium falciparum.

The structure of the glycolytic enzyme class I fructose-1, 6-bisphosphate aldolase from the human malaria parasite Plasmodium falciparum has been determined by X-ray crystallography. Homotetrameric P. falciparum aldolase (PfALDO) crystallizes in space group P3221 with one 80 kDa dimer per asymmetric unit. The final refined PfALDO model has an R-factor of 0.239 and an R-free of 0.329 with respect to data from 8 to 3.0 A resolution. PfALDO is potentially a target for antimalarial drug design as the intraerythrocytic merozoite lifestage of P. falciparum is completely dependent upon glycolysis for its ATP production. Thus, inhibitors directed against the glycolytic enzymes in P. falciparum may be effective in killing the parasite. The structure of PfALDO is compared with the previously determined structure of human aldolase in order to determine possible targets for the structure-based design of selective PfALDO ligands. The salient structural differences include a hydrophobic pocket on the surface of PfALDO, which results from some amino acid changes and a single residue deletion compared with human aldolase, and the overall quaternary structure of the PfALDO tetramer, which buries less surface area than human aldolase.

Amino Acid Sequence↗
PubMed1996

Rapid repetition of the "burst" sequence: the role of diffusion and consequences for imaging.

When the Burst pulse sequence (Hennig et al. MAGMA 1, 39-48 (1993)) is applied with elementary pulses of finite flip angle, a non-uniform longitudinal magnetization is created, in the form of a series of fine bands of saturated spins. Both during and after the pulse train, the molecules contained within these bands diffuse. In this paper a full description is given of the evolution of the non-uniform longitudinal magnetization subsequent to the pulse train and the theory is verified experimentally. The value of the diffusion coefficient influences strongly the signal obtained when the Burst sequence is repeated rapidly. The consequences of this for imaging are discussed and, in particular, for the so-called "frequency-shifted" Burst technique.

Humans↗
PubMed1996

Idiopathic mesenteric varices causing lower gastrointestinal bleeding.

We report a case of lower gastrointestinal bleeding caused by idiopathic mesenteric varices. A 25-year-old man presented with a history of two episodes of lower gastrointestinal bleeding without transfusion. Colonoscopy revealed varices of the entire colon and terminal ileum. Intravariceal blood flow was demonstrated by dopplersonography. Vascular abnormalities were excluded by selective angiography of the upper and lower mesenteric artery. No therapy was given without a new episode of bleeding and there has been no further bleeding to date (a period of 14 months). Mesenteric varices are a rare cause of lower gastrointestinal bleeding, almost always associated with portal hypertension. The varices are idiopathic in only a few cases. The therapy depends on the intensity of bleeding, but resection is the most frequent treatment.

Adult↗
PubMed1995

The use of a PCR-generated invA probe for the detection of Salmonella spp. in artificially and naturally contaminated foods.

Part of the invasion A gene (invA) of slamonellae (Rahn et al., 1992) was amplified and labelled simultaneously with digoxigenin by the polymerase chain reaction (PCR). This was used as gene probe for a colony hybridization assay which included nitrocellulose filter incubation on modified Rambach agar. 312 Salmonella and 268 non-Salmonella strains were hybridized with the invA probe. No false-negative or false-positive results were obtained. In 11 beef samples, which had been contaminated artificially with Salmonella, the test strain was recovered quantitatively with the invA probe. Salmonellae could be detected in 29 samples of 104 further foods of animal origin by means of the gene probe assay in contrast to 27 samples which were positive by the standard method. The invA probe assay allows for the quantitative estimation of Salmonella in fresh meat samples within 48 h. However, with frozen samples a pre-enrichment step is necessary.

Bacterial Proteins↗
PubMed1995

A biotechnological method provides access to aggregation competent monomeric Alzheimer's 1-42 residue amyloid peptide.

Senile plaques, a neuropathological hallmark of Alzheimer's disease, consist primarily of insoluble aggregates of beta-amyloid peptide (A beta). A 42-residue peptide (A beta 1-42) appears to be the predominant form. In contrast to A beta 1-40, A beta 1-42 is characterized by its extreme tendency to aggregate into fibers or precipitate. A tailored biotechnological method prevents aggregation of A beta 1-42 monomers during its production. The method is based on a protein tail fused to the amino terminus of A beta. This tail leads to a high expression in E. coli, and a histidine affinity tag facilitates purification. Selective cleavage of the fusion tail is performed with cyanogen bromide by immobilizing the fusion protein on a reversed phase chromatography column. Cleavage then occurs only at the methionine positioned at the designed site but not at the methionine contained in the membrane anchor sequence of A beta. Furthermore, immobilization prevents aggregation of cleaved A beta. Elution from the HPLC column and all succeeding purification steps are optimized to preserve A beta 1-42 as a monomer. Solutions of monomeric A beta 1-42 spontaneously aggregate into fibers within hours. This permits the investigation of the transition of monomers into fibers and the correlation of physico-chemical properties with biological activities. Mutations of A beta 1-42 at position 35 influence the aggregation properties. Wild-type A beta 1-42 with methionine at position 35 has similar properties as A beta with a methionine sulfoxide residue. The fiber formation tendency, however, is reduced when position 35 is occupied by a glutamine, serine, leucine, or a glutamic acid residue.

Amino Acid Sequence↗
PubMed1994

Comparative study of Lederle/Takeda acellular and Lederle whole-cell pertussis-component diphtheria-tetanus-pertussis vaccines in infants in Germany.

In preparation for a large efficacy trial in Germany, a pilot study was initiated in December 1990. In this study 149 infants were enrolled; with double-blind randomization 75 received Lederle/Takeda acellular pertussis component diphtheria-tetanus-pertussis vaccine (APDT) and 74 received Lederle whole-cell pertussis component diphtheria-tetanus-pertussis vaccine (DTP). The mean age at first dose was 3.5 months, and the second and third doses followed at 6-week intervals. Reactions were relatively mild with both vaccines; in general they were less frequent following APDT. The IgG antibody responses to lymphocytosis promoting factor (LPF) and fimbriae-2 were similar in both groups whereas the responses to pertactin and filamentous haemagglutinin (FHA) were greater in APDT recipients. DTP recipients had greater responses to tetanus and diphtheria toxoids. When age of first dose was examined (8-12 weeks versus 16-20 weeks), it was found that young age had a suppressive effect on antibody responses in DTP but not APDT recipients to LPF toxoid, pertactin, fimbriae-2, and tetanus and diphtheria toxoids. High values of transplacentally acquired antibody lessened the response to LPF toxoid and tetanus toxoid in DTP recipients and to tetanus toxoid in APDT vaccinees. The IgG immune response to LPF toxoid, FHA and fimbriae-2 was found to be more uniform in APDT recipients than in DTP vaccinees. An IgA antibody response to fimbriae-2 was noted in 13% of DTP recipients but in no APDT vaccinees. The broad immunogenicity and mild reactogenicity of this APDT vaccine justifies its use in the German efficacy trial.

Antibodies, Bacterial↗
PubMed1992

A skin MR-marker for radiation treatment planning.

After experiences with fluid filled tubes a gel fitted with an adhesive has been developed, to reproducibly markate treatment ports on the patient's skin. A gel is chosen, that hinders loss of the fluid and smoothly fits to the skin surface due to the adhesive. The clinical use of the gel hopefully will help with the use of NMR image information in radiotherapy treatment planning.

Equipment Design↗