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Biomedical subjects

G Krüger

Publications and source records attributed to G Krüger.

At least 37 records · Page 2Linked to original sources
PubMed1999

[Reconstruction of mediastinal veins in same side dialysis shunt].

Centralvenous obstruction is a rare however typical lesion with patients on chronic hemodialysis. A still functional arteriovenous shunt in its run-in can cause serious disorder, especially painful congestion and an insufficient dialysis. Should the shunt be maintained, a run-off reconstruction is required. 13 patients were treated with a centralvenous obstruction combined with a complication of the shunt. In 8 patients the intervention was either impossible from the beginning or finally proved to be not successful after repeated recanalisations. 6 out of these patients underwent a transsternal reconstruction of their bypass (a total of 7 interventions). 2 patients died perioperatively, 2 patients died 1 year, respectively 1 1/2 years later with a still intact reconstruction, 2 patients are still alive. Their reconstruction has been working for two, respectively three years. The bypass material was large-calibrated e-PTFE with external support. Compared to conventional indications the catheter techniques proved to be less effective in the treatment of central venous obstruction. One year after the first intervention only three out of seven shunts could still be used for the dialysis. The longest symptom-free period was 12 months. The operative reconstruction is indeed very effective but it implies considerable risks and effort. This method cannot be recommended to patients on chronic dialysis who are in a poor condition.

Adult↗
PubMed1998

Physiologic aspects of event related paradigms in magnetic resonance functional neuroimaging.

In order to substantiate event related paradigms in magnetic resonance functional neuroimaging, we assessed the temporal and spatial characteristics of oxygenation-sensitive MRI responses to 1 s periods of visual activation in repetitive protocols. A main finding is a reduction of the functional contrast between conditions (reversing checkerboard vs. darkness) for decreasing interstimulus intervals yielding 4.5% signal change for 89 s, 4% for 9 s, 3% for 6 s, and 1% for 3 s, respectively. Although rapid repetitions of identical stimuli preclude the development of the full positive and negative MRI signal deflections, pertinent responses leave the spatial pattern of activated brain regions unaffected and result in identical maps. These findings suggest the use of interstimulus intervals of the order of the response time from stimulus onset to maximum signal strength (5-6 s in the visual system). The resulting distinction in time will allow for separate mapping of stimulus-related responses with spatially overlapping cortical representations.

Adult↗
PubMed1998

Stimulus dependence of oxygenation-sensitive MRI responses to sustained visual activation.

Oxygenation-sensitive MRI responses to repetitive and sustained visual activation were compared for stimuli with different temporal, spatial, and luminance contrasts, i.e. reversing checkerboard, flashing diffuse red light, and stationary diffuse gray light with darkness as a control. All paradigms elicited an initial oxygenation 'overshoot' as well as a post-stimulus 'undershoot'. However, whereas flashing and stationary diffuse light resulted in more than a 50% decrease of the initial signal response after 6 min of stimulation, checkerboard responsed remained largely unaffected (less than 20% signal attenuation). The demonstration of a stimulus dependence for sustained visual activation reconciles apparently contradictory reports for stimuli involving checkerboards as opposed to goggles, flickerlight, and movies. It may be caused by stimulus-dependent adjustments of neuronal activity, oxygen consumption, blood flow, or blood volume.

Adult↗
PubMed1998

Temporal characteristics of oxygenation-sensitive MRI responses to visual activation in humans.

Series of single-shot blipped echo-planar images with spin-density weighting and T2* sensitivity (2.0 T, TR = 400 ms, TE = 54 ms, flip angle = 30 degrees) were used to study the temporal response profiles to repetitive visual activation (5 Hz, reversing black and white checkerboard versus darkness) for protocols comprising multiple cycles of a 1.6-s stimulus in conjunction with a 8.4-s or 90-s recovery phase and a 10-s stimulus with a 20-s or 90-s recovery phase. Analysis of the real-time data from all activated pixels resulted in a strong positive MRI response (mean values 3-6%) as well as a marked poststimulus undershoot (mean values 1-2%, duration 60-90 s) for all paradigms. Repetitive protocols with insufficient recovery periods of 8.4 s or 20 s gave rise to a wraparound effect when analyzing time-locked averages from multiple activation cycles. This problem may lead to an early signal decrease that originates from the ongoing undershoot of preceding activations folded back into the initial latency phase of a subsequent activation. When ensuring complete decoupling of responses to successive stimuli by using a 90-s recovery period, the wraparound effect vanished and an initial dip was observed in one of seven subjects for a 10-s/90-s protocol.

Adult↗
PubMed1998

The study of Salmonella enteritidis growth kinetics using Rapid Automated Bacterial Impedance Technique.

In order to study strain-specific differences in their growth behaviour at different, and particularly lower, temperatures, generation times for 45 strains of Salmonella enteritidis isolated from food were determined impedimetrically over a temperature range from 7 to 42 degrees C. In practical terms, 7 degrees C is the minimum requirement for Salm. enteritidis growth, and generation time variability increases markedly as this temperature is reached. Reports in the literature describing psychrotrophic behaviour and multiplication at lower temperatures cannot be confirmed. Generation time variability increased as temperature moved away from the optimal range with variation coefficients tending to rise as temperature fell. The great variability of multiplication parameters near the growth limit found in Salm. enteritidis may also be a characteristic of other bacterial species. It is therefore imperative to commence studies on larger numbers of strains to allow prediction of their behaviour at lower temperatures.

Bacteriological Techniques↗
PubMed1997

The developmental activation of the chicken lysozyme locus in transgenic mice requires the interaction of a subset of enhancer elements with the promoter.

The complete chicken lysozyme locus is expressed in a position independent fashion in macrophages of transgenic mice and forms the identical chromatin structure as observed with the endogenous gene in chicken cells. Individual lysozyme cis -regulatory elements reorganize their chromatin structure at different developmental stages. Accordingly, their activities are developmentally regulated, indicating a differential role of these elements in locus activation. We have shown previously that a subset of enhancer elements and the promoter are sufficient to activate transcription of the chicken lysozyme gene at the correct developmental stage. Here, we analyzed to which grade the developmentally controlled chromatin reorganizing capacity of cis -regulatory elements in the 5'-region of the chicken lysozyme locus is dependent on promoter elements, and we examined whether the lysozyme locus carries a dominant chromatin reorganizing element. To this end we generated transgenic mouse lines carrying constructs with a deletion of the lysozyme promoter. Expression of the transgene in macrophages is abolished, however, the chromatin reorganizing ability of the cis -regulatory elements is differentially impaired. Some cis -elements require the interaction with the promoter to stabilize transcription factor complexes detectable as DNase I hypersensitive sites in chromatin, whereas other elements reorganize their chromatin structure autonomously.

Animals↗
PubMed1997

Equivalent responses to lexical and nonlexical visual stimuli in occipital cortex: a functional magnetic resonance imaging study.

Stimulus-related changes in cerebral blood oxygenation were measured using high-resolution functional magnetic resonance imaging sequentially covering visual occipital areas in contiguous sections. During dynamic imaging, healthy subjects silently viewed pseudowords, single false fonts, or length-matched strings of the same false fonts. The paradigm consisted of a sixfold alternation of an activation and a control task. With pseudowords as activation vs single false fonts as control, responses were seen mainly in medial occipital cortex. These responses disappeared when pseudowords were alternated with false font strings as the control and reappeared when false font strings instead of pseudowords served as activation and were alternated with single false fonts. The string-length contrast alone, therefore, is sufficient to account for the activation pattern observed in medial visual cortex when word-like stimuli are contrasted with single characters.

Adult↗
PubMed1997

Bellini duct carcinoma of the kidney--a case report.

Bellini duct carcinoma (BDC), originating from the principal cells of the collecting duct of the kidney, accounts for only 1% of renal carcinomas. This lesion is a histogenetically, morphologically and cytogenetically defined entity. We report an eosinophilic variant of BDC. A 71-year old male presented with a tumor in the right kidney. Nephrectomy was performed. BDC (stage pT3a N0 M0 G2, based on UICC classification) was diagnosed. Electron microscopy revealed an abundance of mitochondria. Intranuclear rodlets were seen. Neuroendocrine differentiation was not demonstrated. After a three-year observation period, there are no signs of recurrence or metastases.

Aged↗
PubMed1996

Genomic position effects lead to an inefficient reorganization of nucleosomes in the 5'-regulatory region of the chicken lysozyme locus in transgenic mice.

The chicken lysozyme locus is gradually activated during macrophage development exhibiting a specific chromatin structure with each differentiation state. Its small size and the extensive characterization of its cis-regulatory elements allows us to study even subtle changes in chromatin structure of the entire gene locus during transcriptional activation. Tissue-specific and position independent expression of the lysozyme locus in transgenic mice requires the cooperation of all cis-regulatory elements. In order to elucidate further the molecular basis of locus activation, we have determined nucleosome positions within the complete 5'-regulatory region of the chicken lysozyme locus in chicken myeloid cell lines and transgenic mice. Each cis-regulatory element develops its unique nucleosomal structure and each one remodels chromatin differently. The nucleosomal organization of the endogenous gene in chicken cell lines and the transgene in the mouse turned out to be identical, enabling us to study the influence of cis-regulatory deletions on the development of an active chromatin structure in transgenic mice. Transgenes with a deletion of an important cis-regulatory element show an impediment in nucleosome reorganization as compared with the complete lysozyme locus. We demonstrate that multicopy transgene-clusters in position dependently expressing mouse lines exhibit a heterogeneous chromatin organization.

Animals↗
PubMed1996

Dynamic uncoupling and recoupling of perfusion and oxidative metabolism during focal brain activation in man.

Changes in glucose consumption, lactate production, and blood oxygenation were measured during prolonged neuronal activation (4-6 min) in human primary visual cortex using dynamic magnetic resonance spectroscopy and imaging. A decrease of steady-state glucose by 40% because of enhanced use by 21% was accompanied by a transient accumulation of lactate with a peak value of 170% 2.5 min after stimulation onset. Rapid blood hyperoxygenation indicating "uncoupling" of blood flow and oxidative metabolism was followed by a return to basal levels over 3 min. Thus, initial nonoxidative glucose consumption during functional activation is gradually complemented by a slower adjustment of oxidative phosphorylation that "recouples" perfusion and oxygen consumption at a new equilibrium.

Adult↗
PubMed1996

Dynamic MRI sensitized to cerebral blood oxygenation and flow during sustained activation of human visual cortex.

Changes in cerebral blood oxygenation and flow during prolonged activation of human visual cortex (6-min video projection) were monitored using high-resolution T2*- and T1-weighted gradient-echo MRI in identical sessions. Oxygenation-sensitive recordings displayed an initial signal increase (oxygenation "overshoot"), a subsequent signal decrease extending over 4-5 min (relative deoxygenation), and a signal drop after the end of stimulation that mirrored the initial response (oxygenation "undershoot"). Flow-sensitive MRI demonstrated that the inflow effect remained elevated during the entire period of stimulation. The observation of gradually decreasing cerebral blood oxygenation, despite persisting elevation of blood flow, may be understood to be an accumulation of deoxyhemoglobin due to the progressive up-regulation of oxidative phosphorylation. The present findings support a concept in which transitions between functional states lead to an uncoupling of perfusion (oxygen delivery) from oxidative metabolism (oxygen consumption) whereas steady-state activity achieves their recoupling.

Adult↗
PubMed1996

Oculocerebrocutaneous syndrome: a case report, a follow-up, and differential diagnostic considerations.

Oculocerebrocutaneous syndrome consists essentially of orbital cysts and microphthalmia/anophthalmia, focal dermal defects, skin appendages and malformations of the central nervous system. Up to now, about 20 sporadic cases have been reported. Limited information is available on the clinical spectrum and on the natural history. We present the long-term follow-up of a 19 year-old patient who was one of the first two patients described by Delleman and Oorthuys in 1981. Furthermore, we report on a new case presenting with bilateral anophthalmia and orbital cysts, typical skin lesions, a complex brain malformation and cleft lip palate. This infant died due to the severe cerebral malformations at the age of 10 months. Encephalocraniocutaneous lipomatosis, focal dermal hypoplasia and microphthalmia with linear skin defects (MLS) syndrome are discussed as the most important differential diagnostic entities.

Adult↗
PubMed1995

Functional MRI of human brain activation combining high spatial and temporal resolution by a CINE FLASH technique.

Functional mapping of human brain activation has been accomplished at high spatial and temporal resolution (voxel size 4.9 microliter, temporal increment 100 ms). The approach was based on oxygenation-sensitive long-echo time FLASH MRI sequences synchronized to multiply repeated cycles of visual stimulation in a CINE acquisition mode. This high temporal resolution revealed that stimulus-related signal intensity changes in human visual cortex display an initial latency followed by increases extending over several seconds. Furthermore, the temporal characteristics of the complete CINE MRI signal time course depended on the absolute and relative durations of activation and control periods and, for example, caused an apparent absence of a poststimulation "under-shoot" phenomenon. Complementing hyperoxygenation due to rapid hemodynamic adjustments, these results suggest signal intensity modulation by enhanced oxygen consumption and concomitant deoxygenation during prolonged and/or repetitive stimulation.

Artifacts↗
PubMed1995

[Müllerian adenosarcoma of the uterus. A case report].

A case of Müllerian adenosarcoma of the uterus is described. The patient, an 81-year old female, was treated in hospital for vaginal bleeding in 1993. She was diagnosed as having a tumour of the uterus. The patient underwent an abdominal hysterectomy with bilateral salpingo-oophorectomy. We found a polypoid intrauterine tumour which had led to a swelling of the cavum and cervical canal. Histologically a Müllerian adenosarcoma was diagnosed. The tumour consisted of a benign glandular component and an mesenchymal component in the form of a low differentiated pleomorphic rhabdomyosarcoma.

Aged↗
PubMed1995

A PCR based X-chromosome inactivation assay for carrier detection in X-linked immunodeficiencies using differential methylation of the androgen receptor gene.

Carrier detection in X-linked immunodeficiencies (X-SCID, WAS, XLA) relies on the demonstration of non-random X inactivation patterns in blood cell lineages. Only a limited number of cells are available after cell separation methods. PCR-based techniques are therefore necessary to analyze active and inactive X chromosomes. Amplifying a polymorphic CAG repeat in the first exon of the androgen receptor gene after selective digestion of the active X chromosome with a methylation-sensitive restriction enzyme allows to distinguish between the paternal and maternal alleles and to identify their methylation status. DNA from B-, T-lymphocytes and total peripheral leukocytes of normal males, females and obligate carriers of X-linked immunodeficiencies were analyzed. The results of this PCR-based X inactivation assay are concordant with the standard methylation studies at the DXS255 locus using Southern blotting. This PCR assay provides a rapid and informative (heterozygosity > 90%) method in carrier detection of X-linked immunodeficiencies and other X-linked disorders, which show non-random X inactivation in cell lineages from the affected tissues.

DNA↗
PubMed1994

Dissection of the locus control function located on the chicken lysozyme gene domain in transgenic mice.

The entire chicken lysozyme gene locus including all known cis-regulatory sequences and the 5' and 3' matrix attachment sites defining the borders of the DNase I sensitive chromatin domain, is expressed at a high level and independent of its chromosomal position in macrophages of transgenic mice. It was concluded that the lysozyme gene locus carries a locus control function. We analysed several cis-regulatory deletion mutants to investigate their influence on tissue specificity and level of expression. Position independent expression of the gene is lost whenever one of the upstream tissue specific enhancer regions is deleted, although tissue specific expression is usually retained. Deletion of the domain border fragments has no influence on copy number dependency of expression. However, without these regions an increased incidence of ectopic expression is observed. This suggests that the domain border fragments may help to suppress transgene expression in inappropriate tissues. We conclude, that position independent expression of the lysozyme gene is not controlled by a single specific region of the locus but is the result of the concerted action of several tissue specific upstream regulatory DNA elements with the promoter.

Animals↗
PubMed1994

Primary mesenchymal tumors of the urinary bladder. A histological and immunohistochemical study of 30 cases.

The light microscopic and immunohistochemical features of 30 primary mesenchymal neoplasms of the urinary bladder are reported. Half of the cases represented smooth and striated muscle tumors (five leiomyomas, seven leiomyosarcomas including epithelioid and myxoid subtypes, one rhabdomyoma, one embryonal rhabdomyosarcoma and one alveolar rhabdomyosarcoma). One third of the tumors were of fibrohistiocytic origin (one fibrous histiocytoma and eight malignant fibrous histiocytomas including fascicular and storiform, inflammatory and pleomorphic subtypes). In addition, a malignant epithelioid schwannoma, a round cell liposarcoma, two hemangiomas and two mixed mesodermal tumors were observed. The morphology of the vesical mesenchymal tumors was identical to that of their counterparts known to occur in other sites, particularly in the soft tissue. Muscle-specific actin, alpha-1-antichymotrypsin, S-100-protein and neuron-specific enolase proved to be useful and reliable immunomarkers for differential diagnosis of poorly differentiated leio- and rhabdomyosarcomas, malignant fibrous histiocytomas and malignant schwannomas. Since some tumors coexpressed several classes of intermediate filaments, diagnostic immunocytochemistry should only be used considering a larger panel of antibodies and in close correlation with the histological and cytological features of the neoplasms.

Adolescent↗