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Biomedical subjects

K Krüger

Publications and source records attributed to K Krüger.

At least 73 records · Page 4Linked to original sources
PubMed1997

Male proportion in offspring of parents exposed to strong static and extremely low-frequency electromagnetic fields in Norway.

Reduced male proportion in offspring of male carbon setters prompted a study into whether offspring of workers exposed to strong static and extremely low-frequency electromagnetic fields (ELF) had a deviant sex ratio. The study was based on all births in Norway 1970-1993. The reference population was offspring of parents not exposed to ELF. The male proportion in offspring of men in aluminum works was 50.38%, RR 0.98 (0.94-1.03), in manganese works 47.32%, RR 0.92 (0.83-1.02), in factories producing iron 50.03%, RR 0.97 (0.93-1.02), in nickel works 48.27%, RR 0.94 (0.84-1.05), and in electric wire production 47.20%, RR 0.92 (0.80-1.05). In the offspring of women in aluminum works, the male proportion was 37.04%, RR 0.72 (0.59-0.90), in all smelter works grouped together, 45.13%, RR 0.88 (0.79-0.99). The male proportion in the reference population was 51.42%. The male proportion in offspring of men in industries with ELF, was slightly reduced, while offspring of women was significantly reduced.

Aluminum↗
PubMed1997

Blood-brain barrier disturbances after rt-PA treatment of thromboembolic stroke in the rat.

We studied the effects of rt-PA (recombinant tissue type-plasminogen activator) treatment on the blood-brain barrier (BBB) after thromboembolic stroke in rat. New MRI methods of diffusion and perfusion imaging to observe the hemodynamic and biophysical effects of thrombolysis were combined with methods for assessment of BBB disturbances. In untreated animals clot embolism produced a rapid drop in MRI perfusion values and the ADC (apparent diffusion coefficient), with subsequent infarction. BBB disturbances, visualised as extravasation of serum proteins on cryostat sections, were manifest in nearly all animals in the borderzone of infarcts. In animals treated with rt-PA 15 min after clot embolism thrombolysis resulted in reperfusion of affected brain regions with subsequent improvement of ADC values. Final lesion size on ADC maps was reduced by 36% relative to untreated animals. However, BBB disturbances were not improved after treatment. To the contrary, rt-PA treated animals showed further regions with serum protein extravasation in the infarcted territories and in distant non-ischemic brain regions. MR imaging with the BBB tracer GdDTPA showed more pronounced and widespread contrast enhancement in the rt-PA treated than in the untreated group. Increased blood-brain barrier disturbances have to be taken into account even when thrombolytic therapy is started very early after the onset of stroke.

Animals↗
PubMed1997

[Juvenile Adamantiades-Behçet disease in decreased stimulation with anti-CD3 monoclonal antibody].

A 12 year old boy developed the complete symptom complex of Adamantiades-Behçet's disease over a two-year period. He presented with the mucocutaneous variant with recurrent to persistent oral ulcers which extended into the pharynx, recurrent genital ulcers, perianal lesions, and a positive pathergy test. Ocular involvement and other symptoms associated with the disease were absent. However, the early onset of the disease and the male gender indicated a bad prognosis. The patients father deficiency of suffered from bronchial asthma with recurrent respiratory infections. An IgG-3 subclass was detected. Lymphocyte transformation tests showed markedly diminished response to stimulation with anti-CD3 monoclonal antibody in both patients, while response to PWM, CoA and PHA was normal. In addition, the concentration of serum soluble interleukin 6 receptor was reduced in both patients.

Antibodies, Monoclonal↗
PubMed1997

Gas vesicle formation in halophilic Archaea.

Gas vesicles are intracellular, microbial flotation devices that consist of mainly one protein, GvpA. The formation of halobacterial gas vesicles occurs along a complex pathway involving 14 different gvp genes that are clustered in a genomic region termed the "vac region". Various vac regions found in Halobacterium salinarum (p-vac and c-vac), Haloferax mediterranei (mc-vac), and Natronobacterium vacuolatum (nv-vac) have been investigated. Except for the latter vac region, the arrangement of the gvp genes is identical. Single gvp genes have been mutated to study the effect on gas vesicle synthesis in transformants and to determine their possible function. Each vac region exhibits a characteristic transcription pattern, and regulatory steps have been observed at the DNA, RNA, and protein level, indicating a complex regulatory network acting during gas vesicle gene expression.

Archaeal Proteins↗
PubMed1997

Low-frequency oscillations of visual, auditory and somatosensory cortical neurons evoked by sensory stimulation.

Low-frequency oscillations-LFOs-below 20 Hz in the activity of cortical neurons are a commonly observed property across all sensory modalities. However, the functional significance and potential role of these intrinsic oscillations are not well understood. Here, we attempt to provide a general framework for the interpretation of this phenomenon by considering its properties across several sensory modalities. In the first part, we provide a survey and a general description of low-frequency oscillations (LFOs) at a cellular level observed following adequate [Basar, and Schürmann, 1994]. Sensory stimulation of neurons recorded in three sensory modalities of neocortices in higher mammals. The second part will address some functional aspects of low-frequency oscillations (LFOs) such as stimulus selectivity and so-called 'interference' phenomena, specifically with findings related to 'resetting' and 'gating' of sensory processing streams. Finally, a hypotheses is outlined in which the low-frequency oscillations are regarded as an organizational principle by which continuity of sensory and motor states over time could be accomplished.

Acoustic Stimulation↗
PubMed1997

[A proposal for the MR staging of early rheumatoid arthritis in the metacarpophalangeal and proximal interphalangeal joints].

PURPOSE: MRI can demonstrate pathology of joint disease in the early course of rheumatoid arthritis prior to destructions seen on conventional radiographs. In a prospective study, we tried to develop a systematical classification of joint pathology demonstrated by MRI, which would be essential for scoring the course of the disease. PATIENTS AND METHOD: Metacarpophalangeal and interphalangeal joints of 48 patients suffering from early rheumatoid arthritis (mean disease duration: 6.4 months) were evaluated by MRI using a high-resolution transmitter-receiver coil. Examinations included 2 mm sliced T2-, T1- and gadolinium enhanced T1-SE sequences in coronal and axial orientation. In consideration of pathological findings on MRI and histopathogenetical pathways of destruction in rheumatoid arthritis a MR-score (0-5) was established. RESULTS: This allowed to score each joint examined: score 0 (normal) in 47.8%/49.5%, score 1 in 35.5%/50.5%, score 2 in 4.2%/0%, score 3 in 10.8%/0%, score 4 in 1.5%/0% of the metacarpophalangeal/interphalangeal joints, respectively. CONCLUSIONS: Using the MR-score a relative individual destruction number can be calculated, which may be used to follow up patients in the early course of rheumatoid arthritis (e.g. drug therapy studies). The presented MR scoring system has to be evaluated further in longitudinal studies and must be correlated to radiographical and clinical findings.

Adult↗
PubMed1997

Nontraumatic subarachnoid hemorrhage: value of repeat angiography.

PURPOSE: To evaluate the benefits and risks of repeat cerebral angiography in patients with subarachnoid hemorrhage of unknown cause. MATERIALS AND METHODS: Findings from 391 angiographic examinations (323 initial, 68 repeat) were retrospectively reviewed in 323 patients with nontraumatic subarachnoid hemorrhage to determine the cause of bleeding and the frequency of complications with neurologic deficit. RESULTS: At the initial angiographic examination, aneurysms were found in 195 patients (60.4%), and arteriovenous malformations were found in 11 patients (3.4%). Sixty-six patients with negative findings at initial examination underwent repeat cerebral angiography. Three additional aneurysms were detected, all of which could be seen retrospectively on the initial angiogram. In 63 patients, the cause of bleeding remained unexplained. Complications of the 391 angiographic examinations were definitive neurologic deficits in one patient (0.2%) and transient deficits in seven patients (1.8%). CONCLUSION: Repeat angiography is not necessary in patients with subarachnoid hemorrhage if technically good, carefully evaluated digital subtraction angiography was performed initially. Repeat angiography seems to be justified only when the initial examination is technically inadequate, when vasospasm is present, or if further bleeding occurs.

Adolescent↗
PubMed1996

The effects of nested primer binding sites on the reproducibility of PCR: mathematical modeling and computer simulation studies.

The polymerase chain reaction (PCR) has become an indispensable tool in modern biological research. Although the application of PCR is a standard routine, we widely lack a theoretical understanding of the dynamic processes involved, especially with respect to the amplification of nonreproducible and/or unexpected amplification products. For one potential source of uncertainty, the presence of nested primer binding sites within an amplifyable DNA locus, we consider a simple stochastic model for the dynamics of PCR amplification of competing products. For commonly used thermostable DNA polymerases lacking a 5'-3'-exonuclease activity, we predict the relative amplification frequencies of competing PCR products dependent on the primer binding probability, the number of PCR cycles, and the number of initial DNA template molecules. At low primer binding probabilities and low numbers of initial DNA template molecules and PCR cycles, we expect the amplification of two products. At high primer binding probabilities and/or high copy numbers of initial template molecules only one main amplification product is predicted at increasing cycle numbers. Furthermore, by means of computer simulation studies we quantify the stochastic variation for the amplification frequencies of competing products.

Bacteriophage lambda↗
PubMed1996

Angiographic detection of gastrointestinal bleeding. An experimental comparison of conventional screen-film angiography and digital subtraction angiography.

RATIONALE AND OBJECTIVES: The authors experimentally assess and compare the detection limit of gastrointestinal bleeding in digital subtraction angiography (DSA) and conventional screen-film angiography. MATERIALS AND METHODS: Arterial blood flow was simulated using a tube model in which bleeding was imitated by exudation of liquid containing contrast material. Gut peristalsis was imitated using silicone tubes filled with air and liquid. Images were acquired by DSA and conventional screen-film angiography. The iodine concentration was increased in increments from 1 mg I/mL, with and without simulated peristalsis, and with both free and circumscribed extravasation of contrast material. RESULTS: The detection limit for free extravasation in DSA was 1 mg I/mL without peristalsis and 60 mg I/mL with peristalsis. The corresponding figures for circumscribed extravasation were 1 mg I/mL and 34 mg I/mL. The detection limit for free extravasation in screen-film angiography was 172 mg I/mL both with and without simulated peristalsis. Circumscribed extravasation was detected at 9 mg I/mL without peristalsis and 7 mg I/mL with peristalsis. CONCLUSION: Digital subtraction angiography is the more sensitive angiographic technique for detection of gastrointestinal bleeding and is superior to conventional screen-film angiography, provided that it is performed with adequate parasym-pathicolysis and suspended respiration. Only when these requirements cannot be achieved is screen-film angiography advantageous.

Angiography↗
PubMed1996

Transcript analysis of the c-vac region and differential synthesis of the two regulatory gas vesicle proteins GvpD and GvpE in Halobacterium salinarium PHH4.

Halobacterium salinarium PHH4 synthesizes gas vesicles in the stationary growth phase by the expression of 14 gyp genes arranged in two clusters. The chromosomal gvpACNO (c-gvpACNO) gene cluster (encoding the major structural gas vesicle protein GvpA and the minor structural protein GvpC was transcribed as three mRNA species starting at one promoter during the stationary phase of growth. The second gene cluster, c-gvpDEFGHIKLM), was transcribed during all stages of growth as a relatively unstable, single mRNA with a maximal length of 6 kb. In addition, a 1.7-kb c-gvpD transcript was synthesized during stationary growth starting at the same promotor as that of the cgvpDEFGHIJKLM mRNA. The expression of the first two genes located in this unit (c-gvpD and c-gvpE) was also monitored by Western blot (immunoblot) analyses using antisera raised against these proteins synthesized in Escherichia coli. While the cGvpD protein was present only during early exponential growth and disappeared during gas vesicle formation, the cGvpE protein was present during cGvpA and gas vesicle synthesis in the early stationary phase of growth. Previous data indicated that cGvpD is involved in repression of gas vesicle formation, whereas cGvpE is a transcriptional activator for the c-gvpA promoter. The appearance of both proteins during the growth cycle is in line with the functions of these proteins in gas vesicle synthesis. The mechanism of the differential translation of cGvpD and cGvpE from the c-gvpDEFGHIJKLM rnRNA still has to be elucidated, but antisense RNAs complementary to the 5' terminus as well as the 3' portion of the c-gvpD mRNA might be involved in this regulation. Such RNAs occurred during early stationary growth when the cGvpD protein level decreased and may possibly inhibit the translation of the c-gvpD mRNA.

Archaeal Proteins↗
PubMed1995

Dimeric 3-phosphoglycerate kinases from hyperthermophilic Archaea. Cloning, sequencing and expression of the 3-phosphoglycerate kinase gene of Pyrococcus woesei in Escherichia coli and characterization of the protein. Structural and functional comparison with the 3-phosphoglycerate kinase of Methanothermus fervidus.

The gene coding for the 3-phosphoglycerate kinase (EC 2.7.2.3) of Pyrococcus woesei was cloned and sequenced. The gene sequence comprises 1230 bp coding for a polypeptide with the theoretical M(r) of 46,195. The deduced protein sequence exhibits a high similarity (46.1% and 46.6% identity) to the other known archaeal 3-phosphoglycerate kinases of Methanobacterium bryantii and Methanothermus fervidus [Fabry, S., Heppner, P., Dietmaier, W. & Hensel, R. (1990) Gene 91, 19-25]. By comparing the 3-phosphoglycerate kinase sequences of the mesophilic and the two thermophilic Archaea, trends in thermoadaptation were confirmed that could be deduced from comparisons of glyceraldehyde-3-phosphate dehydrogenase sequences from the same organisms [Zwickl, P., Fabry, S., Bogedain, C., Haas, A. & Hensel, R. (1990) J. Bacteriol. 172, 4329-4338]. With increasing temperature the average hydrophobicity and the portion of aromatic residues increases, whereas the chain flexibility as well as the content in chemically labile residues (Asn, Cys) decreases. To study the phenotypic properties of the 3-phosphoglycerate kinases from thermophilic Archaea in more detail, the 3-phosphoglycerate kinase genes from P. woesei and M. fervidus were expressed in Escherichia coli. Comparisons of kinetic and molecular properties of the enzymes from the original organisms and from E. coli indicate that the proteins expressed in the mesophilic host are folded correctly. Besides their higher thermostability according to their origin from hyperthermophilic organisms, both enzymes differ from their bacterial and eucaryotic homologues mainly in two respects. (a) The 3-phosphoglycerate kinases from P. woesei and M. fervidus are homomeric dimers in their native state contrary to all other known 3-phosphoglycerate kinases, which are monomers including the enzyme from the mesophilic Archaeum M. bryantii. (b) Monovalent cations are essential for the activity of both archaeal enzymes with K+ being significantly more efficient than Na+. For the P. woesei enzyme, non-cooperative K+ binding with an apparent Kd (K+) of 88 mM could be determined by kinetic analysis, whereas for the M. fervidus 3-phosphoglycerate kinase the K+ binding is rather complex: from the fitting of the saturation data, non-cooperative binding sites with low selectivity for K+ and Na+ (apparent Kd = 270 mM) and at least three cooperative and highly specific K+ binding sites/subunit are deduced. At the optimum growth temperature of P. woesei (100 degrees C) and M. fervidus (83 degrees C), the 3-phosphoglycerate kinases show half-lives of inactivation of only 28 min and 44 min, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1995

Solid-state nuclear magnetic resonance investigations on chlorocyclophosphazenes.

The present study deals with solid-state nuclear magnetic resonance (NMR) investigations on hexachlorocyclotriphosphazene (N3P3Cl6) and T and K form of octachlorocyclotetraphosphazene (N4P4Cl8). Using 31P NMR we have recorded spectra of different magic-angle spinning (MAS) frequencies and static powder spectra. By means of the analysis of spinning sideband intensities the isotropic chemical shifts and the principal values of the chemical shift tensor could be determined. Because of the interactions between phosphorus and the neighbouring chlorine nuclei in the MAS spectra of N3P3Cl6 and N4P4Cl8 more lines were found to exist than was expected with regard to the isotropic chemical shift values according to the crystallographic phosphorus positions. To support this evidence solid-state spectra of the geminally disubstituted compound 2,2,4,4-tetrachloro-6,6-bisthiophenylcyclotriphosphazene [N3P3Cl4(SPh)2] were used. In addition, by means of the individual gauched localized orbitals (IGLO) method 31P NMR chemical shifts, principal values and the orientation of the principal axes of the shielding tensor were calculated for the chlorocyclophosphazenes.

Data Interpretation, Statistical↗
PubMed1995

[Value of computed tomography in the diagnosis of fistulas].

PURPOSE: The purpose of the study was to determine the value of computed tomography (CT) in demonstrating fistulae in comparison with conventional radiographic methods. METHODS: In a prospective study 25 patients were evaluated by conventional radiographic methods and CT. RESULTS: The identification of the fistulous tract was possible with CT in 27 of 29 cases, whereas 2 fistulae could only be detected by indirect signs. Furthermore, CT showed a larger extent of the fistulous tract in 5 patients and revealed complications such as inflammatory mass, abscess or osteomyelitis in 11 cases. CONCLUSION: CT seems to be superior in demonstrating the extent of a fistulous tract and provides valuable information on the surrounding structures.

Adult↗
PubMed1995

Arthritis after hepatitis B vaccination. Report of three cases.

Side effects of hepatitis vaccination are rare. Only a few cases of arthritis after hepatitis vaccination have been published. We report on three cases of vaccination-induced arthritis with different resulting disease. Two cases show the pattern of reactive arthritis. None of them was associated with HLA-B27. In the third case onset of rheumatoid arthritis was triggered by hepatitis vaccination. These three cases show that arthritis after hepatitis B vaccination probably is more common than reported so far, especially in a genetically predisposed subject (two of our patients expressed HLA-DR4).

Adolescent↗
PubMed1994

The timing of processing along the visual pathway in the cat.

We obtained visual response latencies and response durations following visual stimulation of neurones recorded in the lateral geniculate nucleus (LGN), areas 17, 18, 19, the posteromedial lateral suprasylvian sulcus (PMLS), and area 7 of the cat. We found an increasing lengthening of the mean response latencies, consistent with the view of a progressive advance of processing from stage to stage. However, we also observed a substantial and increasing scatter in these latencies. Moreover, response durations vastly supersede this gradual increase in latencies. Taken together, these results suggest that most of the neurones within different stages of a hierarchically organized sensory pathway are simultaneously active when stimulated. Implications of a time-based processing scheme for models of information processing in highly interconnected, multi-layered systems are discussed.

Animals↗
PubMed1994

[The nephroprotective effect of ramipril. Effect on blood pressure and metabolic control in insulin-treated patients with type-2 diabetes mellitus].

AIM: Investigation of the impact of blood pressure and metabolic control on the nephroprotective effect of ramipril in insulin-dependent diabetics. METHOD: Within the framework of an open prospective therapeutic trial, 18 hypertensive, insulin-treated diabetics received ramipril, 5 mg/day, for an average period of 11 months. All the patients had previously received various forms of antihypertensive medication, and had microalbuminuria. RESULTS: Urinary excretion of albumin and N-acetyl-beta-D-glucosaminidase decreased in 13 patients (group 1), but increased in the remaining five patients (group 2). Blood pressure clearly decreased in group 1, but remained constant in group 2. In terms of clinical and biochemical data, the group 2 patients differed from those in group 1, having a lower age, a shorter history of diabetes and higher hemoglobin A1c levels despite higher doses of insulin. CONCLUSIONS: The present observations show that inadequate metabolic control and refractory hypertension in type 2 diabetics accelerate progression of diabetic nephropathy, and may thus negate the nephroprotective effect of the converting enzyme inhibitor, ramipril.

Aged↗