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A Kern

Publications and source records attributed to A Kern.

At least 37 records · Page 2Linked to original sources
PubMed2000

Hydro-MRI in Crohn's disease: appraisal of disease activity.

RATIONALE AND OBJECTIVES: To appraise the value of hydro-MRI in the assessment of activity in Crohn's disease. METHODS: After bowel opacification with 1000 mL of an orally administered 2.5% mannitol solution was achieved, axial and coronal breath-hold sequences (T2-weighted half-Fourier acquisition single-shot turbo spin-echo sequences with or without fat saturation, dynamic T1-weighted fast low-angle shot sequences, and contrast-enhanced T1-weighted fast low-angle shot with fat saturation sequences) were acquired in 82 patients with proved Crohn's disease at 1.0 T. Enhancement of the bowel wall was correlated with other MRI findings, with the Crohn's disease activity index (CDAI), and with levels of C-reactive protein (CRP). RESULTS: In Crohn's disease, contrast enhancement of the affected bowel wall was markedly increased in comparison with the normal bowel wall (+80% +/- 22% versus +43% +/- 12%; P = 3 x 10(-15)). Positive correlations could be established between the increase in bowel wall enhancement and many other MRI findings. Between the increase in bowel wall enhancement and the CDAI, only a poor correlation was found (r = 0.25, P = 0.02). There was no statistical correlation between the increase in bowel wall enhancement and CRP. CONCLUSIONS: Hydro-MRI seems to be superior to the CDAI and CRP for the registration of Crohn's disease activity. In particular, differentiation between an active and an inactive (scarred) stenosis, which is crucial for the choice of therapeutic procedures, seems to be more reliable by the interpretation of several morphological and functional parameters on hydro-MRI than by the use of CDAI and CRP.

Adult↗
PubMed2000

Ergogenic aids.

Explore the source record for details and available documents.

Dietary Supplements↗
PubMed1999

Titration of AAV-2 particles via a novel capsid ELISA: packaging of genomes can limit production of recombinant AAV-2.

We demonstrate the rapid and reliable quantification of physical AAV-2 (adeno-associated virus type 2) particles via a novel ELISA based on a monoclonal antibody which selectively recognizes assembled AAV-2 capsids. Titration of a variety of recombinant AAV-2 (rAAV) preparations revealed that at least 80+percent of all particles were empty, compared with a maximum of 50percent in wild-type AAV-2 stocks, indicating that the recombinant genomes were less efficiently encapsidated. This finding was confirmed upon titration of CsCl gradient fractions from recombinant and wild-type AAV-2 stocks. ELISA-based measurement of capsid numbers revealed a large number of physical particles with low densities corresponding to empty capsids in the recombinant, but not in the wild-type AAV-2 preparations. Moreover, additional expression of VP proteins during rAAV production was found to result in an excessive capsid formation, whilst yielding only minor increases in DNA-containing or transducing rAAV particles. We conclude that encapsidation of viral genomes rather than capsid assembly can be limiting for rAAV production, provided that a critical level of VP expression is maintained. The feasibility of quantifying AAV-2 capsid numbers via the ELISA allows determination of physical to DNA-containing or infectious particle ratios. These are important parameters which should help to optimize and standardize the production and application of recombinant AAV-2.

Antibodies, Monoclonal↗
PubMed1999

[Hydro-MRT with fast sequences in Crohn's disease: a comparison with fractionated gastrointestinal passage].

PURPOSE: To compare the value of hydro-MRI with that of barium studies in patients with Crohn's disease. MATERIALS AND METHODS: After an oral bowel opacification using 1000 ml of a 2.5% mannitol solution, axial and coronal breath-hold sequences (T2W HASTE +/- FS, contrast-enhanced T1W FLASH FS) were acquired in 46 patients with Crohn's disease at 1.0 T. The findings of hydro-MRI were compared with those of barium studies. RESULTS: In the stomach and the small bowel, hydro-MRI and barium studies demonstrated similar numbers of Crohn's involvements (39 vs. 36); in the colon, hydro-MRI showed clearly more affections (23 vs. 10). Hydro-MRI showed 12.7 cm of inflamed bowel per patient, on average (barium studies: 10.4 cm; p = 0.004). There was a good agreement between the two methods regarding the assessment of the extent of Crohn's disease and the severity of bowel stenoses (r = 0.89 and 0.88, respectively). CONCLUSIONS: For the assessment of Crohn's disease, hydro-MRI is preferable to the barium study because of the superior imaging quality and the lack of radiation exposure.

Administration, Oral↗
PubMed1999

Adeno-associated virus type 2 protein interactions: formation of pre-encapsidation complexes.

The nonstructural adeno-associated virus type 2 Rep proteins are known to control viral replication and thus provide the single-stranded DNA genomes required for packaging into preformed capsids. In addition, complexes between Rep proteins and capsids have previously been observed in the course of productive infections. Such complexes have been interpreted as genome-linked Rep molecules associated with the capsid upon successful DNA encapsidation. Here we demonstrate via coimmunoprecipitation, cosedimentation, and yeast two-hybrid analyses that the Rep-VP association also occurs in the absence of packageable genomes, suggesting that such complexes could be involved in the preparation of empty capsids for subsequent encapsidation steps. The Rep domain responsible for the observed Rep-VP interactions is situated within amino acids 322 to 482. In the presence of all Rep proteins, Rep52 and, to a lesser extent, Rep78 are most abundantly recovered with capsids, whereas Rep68 and Rep40 vary in association depending on their expression levels. Rep78 and Rep52 are bound to capsids to roughly the same extent as the minor capsid protein VP2. Complexes of Rep78 and Rep52 with capsids differ in their respective detergent stabilities, indicating that they result from different types of interactions. Rep-VP interaction studies suggest that Rep proteins become stably associated with the capsid during the assembly process. Rep-capsid complexes can reach even higher complexity through additional Rep-Rep interactions, which are particularly detergent labile. Coimmunoprecipitation and yeast two-hybrid data demonstrate the interaction of Rep78 with Rep68, of Rep68 with Rep52, and weak interactions of Rep40 with Rep52 and Rep78. We propose that the large complexes arising from these interactions represent intermediates in the DNA packaging pathway.

Blotting, Western↗
PubMed1999

Frontal bone windows for transcranial color-coded duplex sonography.

BACKGROUND AND PURPOSE: The use of the conventional temporal bone window for transcranial color-coded duplex sonography (TCCS) often results in difficulties in obtaining angle-corrected flow velocity measurements of the A2 segment of the anterior cerebral artery, the posterior communicating artery, and the midline venous vasculature because of the unfavorable insonation angle. The same applies to B-mode imaging of the frontal parenchyma. However, transorbital TCCS raises problems with the insonation of the orbital lens. To overcome these drawbacks, we studied the feasibility of frontal bone windows for TCCS examinations. METHODS: In 75 healthy volunteers (mean age, 45.3+/-17.0 years; age range, 17 to 77 years), the circle of Willis and the venous midline vasculature were insonated through a lateral and paramedian frontal bone window. Insonation quality of parenchymal structures (B-mode) was graded on a 3-point scale depending on the visibility of typical parenchymal landmarks. In a similar manner, the quality of the color-/Doppler-mode imaging of the arteries of the circle of Willis and the internal cerebral veins was assessed. In 15 patients (mean age, 62.7+/-13.7 years; age range, 33 to 83 years), the color-/Doppler-mode imaging quality of the intracranial vessels before and after application of an ultrasound contrast-enhancing agent was compared. RESULTS: B-mode insonation quality was optimal to fair in 73.3% of cases using the lateral and in 52.0% of cases using the paramedian frontal bone window, with defined parenchymal structures used as reference. Insonation quality decreased in those older than 60 years. In those younger than 60 years, angle-corrected flow velocity measurements of the A2 segment of the anterior cerebral artery and the internal cerebral vein were possible in 73.6% and 60.0%, respectively. Contrast enhancement resulted in a highly significant improvement in the imaging quality of the intracranial vessels. CONCLUSIONS: The transfrontal bone windows offer new possibilities for TCCS examinations, although the insonation quality is inferior to the conventional temporal bone window in terms of failure of an acoustic window. This can be compensated for by application of an ultrasound contrast-enhancing agent.

Adolescent↗
PubMed1999

Transcranial color-coded duplex sonography of intracranial veins and sinuses in adults. Reference data from 130 volunteers.

BACKGROUND AND PURPOSE: Transcranial color-coded duplex sonography (TCCS) of intracranial veins and sinuses in adults is a new, emerging application of ultrasonographic imaging. This study reports a standardized examination protocol for venous TCCS and provides reference data for clinical application. METHODS: In 130 healthy volunteers (mean age, 45.9+/-16.9 years; range, 14 to 77 years) the intracranial venous system was examined using frequency-based transtemporal TCCS. Identification rate, blood flow velocity, resistance index, and systolic/diastolic ratio were recorded for each examined venous vessel. RESULTS: Intracranial veins and sinuses show a low pulsatile forward flow with maximal systolic blood flow velocity up to 20 cm/s. Significant side differences of blood flow velocity in the paired venous structures could not be detected. Venous flow velocities decreased with age, whereas resistance indices and systolic/diastolic ratios increased. Women showed higher flow velocities than men. Mean identification rates for all age groups ranged from 70% to 90% for the deep middle cerebral vein, the basal cerebral vein, and the great cerebral vein of Galen. The straight sinus, the transverse sinus, and the rostral part of the superior sagittal sinus could be detected in 55% to 70% of cases. Detection rates were dependent on age and decreased as age increased. CONCLUSIONS: Venous TCCS can reliably image a significant part of the cerebral venous system. This method can provide information on venous hemodynamics in normal subjects and pathological cases.

Adolescent↗
PubMed1998

Novel tools for production and purification of recombinant adenoassociated virus vectors.

Standard protocols for the generation of adenoassociated virus type 2 (AAV-2)-based vectors for human gene therapy applications require cotransfection of cells with a recombinant AAV (rAAV) vector plasmid and a packaging plasmid that provides the AAV rep and cap genes. The transfected cells must also be overinfected with a helper virus, e.g., adenovirus (Ad), which delivers multiple helper functions necessary for rAAV production. Therefore, rAAV stocks produced using these protocols are contaminated with helper adenovirus. The generation of a novel packaging/helper plasmid, pDG, containing all AAV and Ad functions required for amplification and packaging of AAV vector plasmids, is described here. Cotransfection of cells with pDG and an AAV vector plasmid was sufficient for production of infectious rAAV, resulting in helper virus-free rAAV stocks. The rAAV titers obtained using pDG as packaging plasmid were up to 10-fold higher than those achieved using conventional protocols for rAAV production. Replacement of the AAV-2 p5 promoter by an MMTV-LTR promoter in pDG led to reduced expression of Rep78/68; however, expression of the VP proteins was significantly increased compared with VP levels from standard packaging plasmids. Immunofluorescence analyses showed that the strong accumulation of VP proteins in pDG-transfected cells resulted in enhanced AAV capsid assembly, which is limiting for efficient rAAV production. Furthermore, using a monoclonal antibody highly specific for AAV-2 capsids (A20), an rAAV affinity purification procedure protocol was established. The application of the tools described here led to a significant improvement in recombinant AAV vector production and purification.

Capsid↗
PubMed1998

Role of the I-domain in collagen binding specificity and activation of the integrins alpha1beta1 and alpha2beta1.

Adhesion to collagens by most cell types is mediated by the integrins alpha1beta1 and alpha2beta1. Both integrin alpha subunits belong to a group which is characterized by the presence of an I domain in the N-terminal half of the molecule, and this domain has been implicated in the ligand recognition. Since purified alpha1beta1 and alpha2beta1 differ in their binding to collagens I and IV and recognize different sites within the major cell binding domain of collagen IV, we investigated the potential role of the alpha1 and alpha2 I domains in specific collagen adhesion. We find that introducing the alpha2 I domain into alpha1 results in surface expression of a functional collagen receptor. The adhesion mediated by this chimeric receptor (alpha1-2-1beta1) is similar to the adhesion profile conferred by alpha2beta1, not alpha1beta1. The presence of alpha2 or alpha1-2-1 results in preferential binding to collagen I, whereas alpha1 expressing cells bind better to collagen IV. In addition, alpha1 containing cells bind to low amounts of a tryptic fragment of collagen IV, whereas alpha2 or alpha1-2-1 bearing cells adhere only to high concentrations of this substrate. We also find that collagen adhesion of NIH-3T3 mediated by alpha2beta1 or alpha1-2-1beta1, but not by alpha1, requires the presence of Mn2+ ions. This ion requirement was not found in CHO cells, implicating the I domain in cell type-specific activation of integrins.

3T3 Cells↗
PubMed1998

[Radiotherapy of humero-scapular periarthritis using ultra-hard photons. Evaluation by MRI findings].

PURPOSE: Evaluation of MRI in radiotherapy of humeroscapular periarthritis. PATIENTS AND METHODS: Seventy-seven patients with humeroscapular periarthritis prospectively underwent MRI before radiotherapy. RESULTS: Six months after radiotherapy, 34% of the patients had achieved complete pain relief, 35% major pain relief. Twenty percent had only slight improvement and 12% no improvement. Positive correlation of radiotherapy outcome and MRI findings could be shown for acute tendinitis, erosions, and complete and incomplete ruptures of the supraspinatus tendon. CONCLUSIONS: Radiotherapy is highly effective in the treatment of humeroscapular periarthritis. The indication can be improved using MRI.

Aged↗
PubMed1998

Soluble and cell surface ICAM-1 as markers for disease activity in multiple sclerosis.

OBJECTIVE: The intercellular adhesion molecule-1 (ICAM-1) is a member of the Ig supergene family. ICAM-1 is expressed on various cells like peripheral blood lymphocytes, endothelial cells or thymic cells and the cell surface form is supposed to be shed into a soluble form. The expression of ICAM-1 is induced by cytokines like Interleukin-1, TNF alpha or interferon gamma. The aim of the study was to investigate whether changes of cell surface and soluble ICAM-1 in the cerebrospinal fluid (CSF) and blood are indicative for disease activity in patients with multiple sclerosis (MS). MATERIAL AND METHODS: In all patients with relapsing-remitting MS (relapse: n=31, remission: n=11) and controls (n=13) the expression of cell surface ICAM-1 (c-ICAM-1) was determined by two colour flow cytometry. Soluble ICAM-1 (s-ICAM-1) was measured by ELISA. Follow-up examinations were done 3 months later. RESULTS: In 31 patients with a current relapse we found significantly decreased expression levels of c-ICAM-1 on leukocytes in CSF (P<0.001) and blood (P<0.10), when compared to those 11 individuals experiencing remission. In contrast we observed significantly (P<0.05) increased levels of s-ICAM-1 in CSF of patients with relapses. Comparing patients who had been in remission for more than 4 weeks (n=11) with remission lasting longer than 3 months (n=28) we detected stable c-ICAM-1 expression on CD3+ T cells in blood. CONCLUSION: Our results demonstrate for the first time that c-ICAM-1 on CD3+ T-cells in CSF and blood is an activity marker in MS.

Adolescent↗
PubMed1998

Biotransformation of cerivastatin in mice, rats, and dogs in vivo.

Biotransformation of cerivastatin was investigated in mice, rats, and dogs in vivo using the 14C-labeled drug. Marked species differences exist, both in pathways and extent of cerivastatin metabolism. Unchanged drug, together with its lactone, predominates in dog plasma and represents 40% of the dose in the excreta, whereas in rat bile they account for approximately 10% of the dose. In mice, the drug is metabolized rapidly and almost completely. Biotransformation of cerivastatin occurs by three distinct phase I routes and by phase II conjugation with sugar-type moieties and taurine. Phase I routes are demethylation of the pyridinyl methyl ether, beta-oxidation of the 3,5-dihydroxy acid side chain, and reductive removal of the side chain 3-hydroxy group. In dogs, demethylation is the dominating phase I biotransformation. Phase II conjugation is equally important. In dog bile, different regioisomeric drug glucuronides and the benzylic glucuronide and glucoside conjugate of the demethylated drug were found. In rats, besides demethylation, beta-oxidation of the dihydroxy acid side chain-followed by reductive removal of the 5-hydroxy group-is the major reaction. The resulting pentenoic acid derivatives are observed in plasma and liver homogenate. These metabolites are subsequently conjugated with taurine and excreted in the bile. This metabolic sequence is also important in mice. Furthermore, only in mice, cerivastatin is subject to reductive removal of the 3-hydroxy group, together with demethylation. The 5-hydroxyheptenoic acids formed predominate in plasma and liver homogenate, whereas the corresponding taurine conjugates are excreted in the bile.

Animals↗
PubMed1997

Drug metabolism in hepatocyte sandwich cultures of rats and humans.

Adult hepatocytes from rat and man were maintained for 2 weeks between two gel layers in a sandwich configuration to study the influence of this culture technique on the preservation of basal activities of xenobiotic-metabolizing phase I and phase II enzymes. The response of these enzyme activities to an enzyme inducer was investigated using rifampicin (RIF). Basal levels of cytochrome P-450 (CYP) isozymes were characterized by measuring ethoxyresorufin O-deethylation (EROD), ethoxycoumarin O-deethylation (ECOD), and the specific oxidation of testosterone (T). In hepatocytes from untreated rats, CYP isozyme levels, including the major form CYP 2C11, increased during the first 3 days in culture. After this period of recovery, the levels of CYP 2C11, CYP 2A1, and CYP 2B1 decreased, whereas CYP 3A1 increased. In contrast to these dynamic changes, CYP activities such as CYP 1A2 and the major isozyme CYP 3A4 were largely preserved until day 9 in cultures of human hepatocytes. In measuring phase II activities, a distinct increase in glucuronosyltransferase (UDP-GT) activity toward p-nitrophenol (PNP) was found for rat and human hepatocytes over 2 weeks in culture. Sulfotransferase (ST) activity toward PNP showed an initial increase, with a maximum at day 7 and day 9 in culture, respectively, and then decreased until day 14. Glutathione S-transferase (GST) activity decreased constantly during the time of culture. Effects of the enzyme-inducing drug rifampicin on phase I and phase II enzymes were investigated using cultured human hepatocytes. Rifampicin treatment (50 micromol/L) for 7 days resulted in a 3.7-fold induction of CYP 3A4 at day 9 in culture. ECOD activity was increased sixfold and phase II ST activity increased twofold compared to the initial value at day 3. No effect of rifampicin on CYP 3A was found in cultures of rat hepatocytes. These results demonstrate that rat and human hepatocytes preserve the major forms of CYP isozymes and phase II activities and respond to inducing drugs such as rifampicin. The novel hepatocyte sandwich culture is suitable for investigating drug metabolism, drug-drug interactions and enzyme induction.

Adult↗
PubMed1997

Prevalence of antibodies to Borrelia burgdorferi and tick-borne encephalitis virus in an endemic region in southern Germany.

With the intention to evaluate the frequency of asymptomatic infections with TBE virus and B. burgdorferi clinical data and serum specimens were collected from 393 individuals living in an area endemic for both agents (Freiburg, southern Germany). Sera were examined by ELISA. Borderline and positive results were checked by immunoblotting. Only specific antibodies detected by immunoblotting (B. burgdorferi: 22 kDa, 31 kDa, 34 kDa, 39 kDa, 83 kDa; TBE: glycoprotein E) were assessed as positive findings. Specific antibodies to B. burgdorferi were detected in 17/105 individuals with possible symptoms of borreliosis (16%) and in 36/288 individuals without current or previous symptoms of borreliosis (12.5%). Antibody to TBE virus was demonstrated in 34/361 individuals (9.4%) without clinical symptoms of TBE or vaccination against TBE. Thirty individuals had been immunised against TBE (10.6%) and two had clinical TBE one year ago. Antibodies against both agents were detected only in 1.5% of all subjects. Considering the low seroprevalence, antibody screening is not recommended prior to TBE vaccination.

Antibodies, Bacterial↗
PubMed1997

Acanthocheilonema viteae: vaccination with irradiated L3 induces resistance in three species of rodents (Meriones unguiculatus, Mastomys coucha, Mesocricetus auratus).

Three species of rodents were immunized with 50 irradiated (35 krad) stage-3 larvae (L3) of the filaria Acanthocheilonema viteae and challenged with an infection of normal L3. The immunization induced a significant reduction of the worm burden developing from the challenge infection in all host species, the jird (Meriones unguiculatus), the multimammate rat (Mastomys coucha) and the golden hamster (Mesocricetus auratus). The induced resistance was highest in jirds (92.5 +/- 9.7) followed by golden hamsters (59.4 +/- 26.6) and multimammate rats (55.1 +/- 40.4). The time course of antibody response against antigens of L3, adult worms and microfilariae, as studied by ELISA, showed quantitative and qualitative differences between the species. The antibody response against L3 antigens in immunoblots was similar in all species. Only one of the golden hamsters developed an antibody response against the surface of vector derived L3, while sera of jirds and multimammate rats did not react with L3 surface.

Animals↗
PubMed1997

Subcellular compartmentalization of adeno-associated virus type 2 assembly.

Using immunofluorescence and in situ hybridization techniques, we studied the intracellular localization of adeno-associated virus type 2 (AAV-2) Rep proteins, VP proteins, and DNA during the course of an AAV-2/adenovirus type 2 coinfection. In an early stage, the Rep proteins showed a punctate distribution pattern over the nuclei of infected cells, reminiscent of replication foci. At this stage, no capsid proteins were detectable. At later stages, the Rep proteins were distributed more homogeneously over the nuclear interior and finally became redistributed into clusters slightly enriched at the nuclear periphery. During an intermediate stage, they also appeared at an interior part of the nucleolus for a short period, whereas most of the time the nucleoli were Rep negative. AAV-2 DNA colocalized with the Rep proteins. All three capsid proteins were strongly enriched in the nucleolus in a transient stage of infection, when the Rep proteins homogeneously filled the nucleoplasm. Thereafter, they became distributed over the whole nucleus and colocalized in nucleoplasmic clusters with the Rep proteins and AAV-2 DNA. While VP1 and VP2 strongly accumulated in the nucleus, VP3 was almost equally distributed between the nucleus and cytoplasm. Capsids, visualized by a conformation-specific antibody, were first detectable in the nucleoli and then spread over the whole nucleoplasm. This suggests that nucleolar components are involved in initiation of capsid assembly whereas DNA packaging occurs in the nucleoplasm. Expression of a transfected full-length AAV-2 genome followed by adenovirus infection showed all stages of an AAV-2/adenovirus coinfection, whereas after expression of the cap gene alone, capsids were restricted to the nucleoli and did not follow the nuclear redistribution observed in the presence of the whole AAV-2 genome. Coexpression of Rep proteins released the restriction of capsids to the nucleolus, suggesting that the Rep proteins are involved in nuclear redistribution of AAV capsids during viral infection. Capsid formation was dependent on the concentration of expressed capsid protein.

Cell Compartmentation↗
PubMed1997

Metabolism of cerivastatin by human liver microsomes in vitro. Characterization of primary metabolic pathways and of cytochrome P450 isozymes involved.

Biotransformation of cerivastatin, a new cholesterol-lowering drug, by human liver microsomes was investigated using the 14C-labeled drug. Metabolite profiles were established by HPLC and structures of metabolites were elucidated. Two metabolic pathways were equally important, demethylation of the benzylic methyl other and hydroxylation at one methyl group of the 6-isopropyl substituent. The product of combined hydroxylation and demethylation was observed as a minor metabolite. During sample preparation the lactone forms of both primary metabolites were isolated in small amounts. Detailed structural analysis by NMR and LC-ESI-MS showed that hydroxylation occurred with high regio- and stereoselectivity. The proposed structures were confirmed by chemical synthesis of enantiomerically pure reference compounds. Microsomes from a human lymphoblastoid AHH-1 cell line, stably expressing CYP 3A4, catalyzed the demethylation reaction. Upon incubation of cerivastatin with human liver microsomes in the presence of the specific CYP 3A inhibitor TAO, both hydroxylation and demethylation were considerably reduced. This indicates that CYP 3A enzymes play a major role in cerivastatin metabolism.

Anticholesteremic Agents↗