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At least 1,261 records · Page 70Linked to original sources

PubMed1999

The isocitrate dehydrogenase kinase/phosphatase from Escherichia coli is highly sensitive to in-vitro oxidative conditions role of cysteine67 and cysteine108 in the formation of a disulfide-bonded homodimer.

Isocitrate dehydrogenase kinase/phosphatase (IDHK/P) is a homodimeric enzyme which controls the oxidative metabolism of Escherichia coli, and exibits a high intrinsic ATPase activity. When subjected to electrophoresis under nonreducing conditions, the purified enzyme migrates partially as a dimer. The proportion of the dimer over the monomer is greatly increased by treatment with cupric 1,10 phenanthrolinate or 5,5'-dithio-bis(2-nitrobenzoic acid), and fully reversed by dithiothreitol, indicating that covalent dimerization is produced by a disulfide bond. To identify the residue(s) involved in this intermolecular disulfide-bond, each of the eight cysteines of the enzyme was individually mutated into a serine. It was found that, under nonreducing conditions, the electrophoretic patterns of all corresponding mutants are identical to that of the wild-type, except for the Cys67-->Ser which migrates exclusively as a monomer and for the Cys108-->Ser which migrates preferentially as a dimer. Furthermore, in contrast to the wild-type enzyme and all the other mutants, the Cys67-->Ser mutant still migrates as a monomer after treatment with cupric 1,10 phenanthrolinate. This result indicates that the intermolecular disulfide bond involves only Cys67 in each IDHK/P wild-type monomer. This was further supported by mass spectrum analysis of the tryptic peptides derived from either the cupric 1,10 phenanthrolinate-treated wild-type enzyme or the native Cys108-->Ser mutant, which show that they both contain a Cys67-Cys67 disulfide bond. Moreover, both the cupric 1,10 phenanthrolinate-treated wild-type enzyme and the native Cys108-->Ser mutant contain another disulfide bond between Cys356 and Cys480. Previous results have shown that this additional Cys356-Cys480 disulfide bond is intramolecular [Oudot, C., Jault, J.-M., Jaquinod, M., Negre, D., Prost, J.-F., Cozzone, A.J. & Cortay, J.-C. (1998) Eur. J. Biochem. 258, 579-585].

Base Sequence↗

PubMed1990

Alpha rhythm in classical migraine (migraine with aura): abnormalities in the headache-free interval.

The alpha rhythm of 18 patients with classical migraine (migraine with aura) was studied by EEG spectrum analysis for evidence of neural abnormalities during the asymptomatic period. The temporal relationship of the findings to attacks was studied by serial records in 11 cases. Increased frequency dispersion and frequency asymmetries of the alpha rhythm were found. The records were, however, mostly normal when separated from attacks by at least 10 asymptomatic days. The abnormalities increased significantly before the onset of prodromal symptoms and clearly outlasted the headache phase. The results give evidence of a fluctuating asymmetric neural disorder in classical migraine.

Adult↗

PubMed2001

Selective pick-up of increased iron by deferoxamine-coupled cellulose abrogates the iron-driven induction of matrix-degrading metalloproteinase 1 and lipid peroxidation in human dermal fibroblasts in vitro: a new dressing concept.

Using atomic absorption spectrum analysis, we found iron levels in exudates from chronic wounds to be significantly increased (3.71 +/- 1.56 micromol per g protein) compared to wound fluids from acute wounds derived from blister fluids (1.15 +/- 0.62 micromol per g protein, p < 0.02), drainage fluids of acute wounds (0.87 +/- 0.34 micromol per g protein, p < 0.002), and pooled human plasma of 50 volunteers (0.42 micromol per g protein). Increased free iron and an increase in reactive oxygen species released from neutrophils represent pathogenic key steps that --via the Fenton reaction - are thought to be responsible for the persistent inflammation, increased connective tissue degradation, and lipid peroxidation contributing to the prooxidant hostile microenvironment of chronic venous leg ulcers. We herein designed a selective pick-up dressing for iron ions by covalently binding deferoxamine to cellulose. No leakage occurred following gamma sterilization of the dressing and, more importantly, the deferoxamine-coupled cellulose dressing retained its iron complexing properties sufficient to reduce iron levels found in chronic venous ulcers to levels comparable to those found in acute wounds. In order to study the functionality of the dressing, human dermal fibroblasts were exposed to a Fenton reaction mimicking combination of 220 microM Fe(III) citrate and 1 mM ascorbate resulting in a 4-fold induction of matrix-degrading metalloproteinase 1 as determined by a matrix-degrading metalloproteinase 1 specific enzyme-linked immunosorbent assay. This induction was completely suppressed by dissolved deferoxamine at a concentration of 220 microM or by an equimolar amount of deferoxamine immobilized to cellulose. In addition, the Fe(III) citrate and ascorbate driven Fenton reaction resulted in an 8-fold increase in malondialdehyde, the major product of lipid peroxidation, as determined by high pressure liquid chromatography. This increase in malondialdehyde levels could be significantly reduced in the presence of the selective pick-up dressing coupled with deferoxamine suggesting that the deferoxamine dressing, in fact, prevents the development of a damaging prooxidant microenvironment and also protects from unfavorable consequences like matrix-degrading metalloproteinase 1 and lipid peroxide induction.

Bandages↗

PubMed1985

[Ultrasonic Doppler method for noninvasive determination of fetal blood flow volumes].

Fetal blood flow volume and unteroplacental flow profiles can be measured with a linear real time scanner in conjunction with a pulsed Doppler system. It was the aim of this study to simulate the blood flow volume under varying experimental conditions by using an in-vitro model, and to examine and compare pulsed Doppler equipments. Defined flow rates between 200 and 1200 ml/min were pumped via a tygon tube placed in a liquid bath. The sample volume was kept constant, the depths of the tube were varied. Processing of the Doppler signals was done by spectrum analysis. There was a good correlation between true and ultrasonically measured flow rates (r = 0.96-1). However, particularly low flow rates resulted in an overestimation of blood flow when using high-pass filtering for avoiding Doppler signals arising from the vessel wall. These errors probably not only depend on the flow profiles, but also on the measuring techniques involved with the individual instruments. The effect of high-pass filtering must be taken into account when interpreting the results, particularly in the case of low-flow rates.

Blood Flow Velocity↗

PubMed1984

[Simulation of arterial pulse curves in elastic tubes and a carotid preparation].

Results of Doppler sonographic examination of the arteries in the neck are not completely comparable to angiographical findings, because the application of the Doppler probe is not standardised and angiography does not demonstrate the exact vascular morphology. To experimentally correlate the Doppler-findings with morphology, a flow rig was constructed that generated within elastic tubes as well as human carotid artery specimens all types of human arterial pulse curves (e.g. subclavian or internal carotid artery). This was achieved by taking into account the principles of pulse wave propagation and reflection in vivo. A degassed aqueous suspension of amylum maidis was used as circulating medium. This flow rig allows the evaluation of the diagnostic criteria of Doppler spectrum analysis, such as peak frequencies and spectral broadening. Testing the characteristics of Doppler equipment is another useful application.

Blood Pressure↗

PubMed1994

[Transvaginal color-coded Doppler ultrasound in ovarian tumors].

In 129 patients with ovarian tumours, a preoperative examination by transvaginal colour Doppler sonography (ATL UM9 HDI) was performed. 45 were malignant and 84 benign. 46 patients were premenopausal and 83 postmenopausal. All tumour vessels were analysed by spectrum analysis. The number of tumour vessels and the lowest resistance index (RImin) and pulsatility index (PImin) of all vessels were evaluated as diagnostic criteria of the neovascularisation. Up to 19 vessels were found in 115 (89%) tumours. In benign lesions, the number of vessels was significantly lower than in malignancies (median 3 versus 9, p < 0.0001). The RImin and PImin values between benign and malignant tumours were also significantly different, independent of the menopausal status. In postmenopausal patients, the median RImin in 42 benign tumours was 0.62 (0.26-1.0) and in 41 malignancies 0.40 (0.22-0.66). The median PImin was 0.98 (0.31-5.84) in benign tumours and 0.53 (0.25-1.22) in malignant tumours. However, due to the overlapping range between benign and malignant tumours, these parameters do not allow an accurate differentiation. With a cut off value for RImin = 0.5 and PImin = 0.7, the sensitivity is 85% or 82.5% respectively. The specificity for RImin and PImin is 77%, and the diagnostic accuracy is 84% and 80% respectively. The correlation coefficient between RImin and PImin is 0.99 in benign and malignant tumours and both indices are adequate. The calculation of the RI is more easily available and should be preferred as a diagnostic parameter.

Adolescent↗

PubMed1990

Increased 137caesium whole body radioactivity in high-performance athletes.

A shadow shield whole body counter with automated gamma spectrum analysis is used in the division of nuclear medicine for the measurement of whole body radioactivity. After the radioactive fall-out in Austria caused by the Chernobyl accident the instrument has been extensively utilized for the assessment of the radiation level in the general population. In November of 1986 and 1987 the level of internal contamination with 137Cs in high-performance athletes was compared with a group of subjects practicing little or no sports. It was found that significantly higher contents of 137Cs were present in the athletes. Furthermore, it was found that within the groups of athletes male subjects had significantly higher internal 137Cs contamination per kilogram of body mass than the female subjects. An explanation for this is the different nutrition and the higher relative muscle mass of the athletes.

Adolescent↗

PubMed1989

[Follow-up monitoring of kidney transplants with color-coded duplex sonography].

Fifty patients were examined immediately after renal transplantation by colour-coded duplex sonography. This procedure is a further development of conventional duplex sonography and permits demonstration of soft tissues in real time, as well as simultaneous imaging of blood flow over the whole imaging area. Perfusion of the transplant could be demonstrated in all patients by this method. Colour-coded duplex sonography can replace scintigraphy and angiography for the demonstration of perfusion of renal transplants. It is, however, not possible to distinguish with certainty between acute tubular necrosis and acute rejection by performing spectrum analysis of blood flow in the renal arteries.

Adolescent↗

PubMed1989

[Diagnostic value of angiodynography in pulsating space-occupying lesions].

19 patients with undiagnosed pulsating masses occurring after angiography, by-pass surgery or trauma were examined by conventional ultrasound, duplex sonography, angiodynography and, in some cases, by angiography. There were nine pseudo-aneurysms and 13 haematomas; in each case the diagnosis was made by duplex sonography and by angiodynography. Pseudoaneurysms show the following typical signs on angiodynography: 1. Typical wave form during spectrum analysis, 2. Specific blood-flow pattern into and out of the aneurysm, 3. Turbulence within the aneurysm. Angiodynography provides a reliable, rapid and exact means of diagnosis. In future, this will be able to replace more invasive procedures such as angiography.

Aneurysm↗

PubMedDate not supplied

[The role of the alloy-specific elements iron, cobalt, chromium and nickel in aseptic loosening of total hip joint prosthesis].

The cause of aseptic loosening of total hip joint prostheses is still largely unexplained. In addition to mechanical forces, material factors may also be instrumental. In 16 patients with loosened hip prostheses who underwent re-operation (8 X Huggler-Weber, 8 X McKee-Farrar), the concentration of the alloy-specific elements cobalt, chromium, nickel and iron were determined in 58 tissue samples by means of neutron activation and emission spectrum analysis. An increase in the element concentrations was found in all the tissue samples, and this was unrelated to the time elapsed since implantation. The chromium concentration in particular was significantly elevated in all the tissue samples, in some patients with McKee-Farrar prostheses up to 10,000 times the norm. In view of the known toxicity of cobalt, chromium and nickel in high doses it seems that the presence of unphysiologically high concentrations of these elements in the vicinity of total hip joint prostheses represents an explanation of some of the loosened prostheses.

Chromium Alloys↗

PubMed1988

Intraoperative duplex scanning after carotid artery reconstruction: a valuable tool.

The operative management of extracranial cerebrovascular occlusive disease requires meticulous surgical technique. Intraoperative duplex imaging (10 MHz B-mode ultrasound combined with 7.5 MHz Doppler spectrum analysis) was used in an attempt to recognize technical problems that might result in serious neurologic injury. Eighty-four carotid arteries were studied in 76 consecutive patients undergoing carotid endarterectomy or reconstruction. Indications for operation included carotid territory transient ischemic attack (n = 36 [43%]), amaurosis fugax (n = 16 [19%]), stroke (n = 11 [13%]), asymptomatic stenosis (n = 11 [13%]), vertebrobasilar transient ischemic attack (n = 7 [8%]), recurrent stenosis (n = 2 [2%]), and trauma (n = 1 [1%]). Arterial anatomy was assessed ultrasonographically and duplex-derived velocity measurements were obtained to assess hemodynamics. Increased velocity measurement was noted to correlate with ultrasound image of stenosis. Technical errors were identified in 17 patients (22%), including six persons with residual internal carotid artery stenoses, three persons with hemodynamically significant stenoses caused by "kinked" internal carotid arteries, eight persons with debris or intimal flaps in their external carotid arteries, and one person with an occluded external carotid artery. The intraoperative duplex scan led to corrective measures during the surgical procedure in eight patients (11%). No new ipsilateral brain injury was noted in the 76 patients postoperatively. Intraoperative duplex scanning accurately identified residual stenosis, intraluminal thrombus, and loose debris. Duplex scanning altered intraoperative decision making in a significant proportion of patients studied.

Carotid Arteries↗

PubMed1989

Duplex ultrasound scanning in the assessment of arteriovenous fistulas created for hemodialysis access: comparison with digital subtraction angiography.

The results of duplex ultrasound scanning for the diagnosis of stenoses in Brescia-Cimino arteriovenous fistulas and graft arteriovenous fistulas created for hemodialysis access are reported. Quantitative Doppler spectrum analysis of 64 arteriovenous fistulas was correlated with the outcome of digital subtraction angiography. The best Doppler parameter for the detection of a stenosis was the peak systolic frequency. In graft arteriovenous fistulas the use of this parameter resulted in a diagnostic accuracy of 86%, a sensitivity of 92%, and a specificity of 84% in the detection of stenoses. In Brescia-Cimino arteriovenous fistulas the diagnosis of anastomotic stenoses was possible with a diagnostic accuracy of 81%, a sensitivity of 79%, and a specificity of 84%. Measurement of peak systolic frequency ratios or end-diastolic frequencies had no additional diagnostic value for the detection of stenoses. The diagnosis of efferent vein stenoses was very accurate with duplex investigation (accuracy 96%, sensitivity 95%, and a specificity of 97%. We conclude that duplex scanning is a promising noninvasive method for the diagnosis of stenoses in arteriovenous fistulas created for hemodialysis access.

Adult↗

PubMed2004

DNA heterogeneity and phosphorylation unveiled by single-molecule electrophoresis.

Broad-spectrum analysis of DNA and RNA samples is of increasing importance in the growing field of biotechnology. We show that nanopore measurements may be used to assess the purity, phosphorylation state, and chemical integrity of nucleic acid preparations. In contrast with gel electrophoresis and mass spectrometry, an unprecedented dynamic range of DNA sizes and concentrations can be evaluated in a single data acquisition process that spans minutes. Because the molecule information is quantized and digitally recorded with single-molecule resolution, the sensitivity of the system can be adjusted in real time to detect trace amounts of a particular DNA species.

DNA↗

PubMed2006

beta-Amyloid infusion results in delayed and age-dependent learning deficits without role of inflammation or beta-amyloid deposits.

beta-Amyloid (Abeta) polypeptide plays a critical role in the pathogenesis of Alzheimer's disease (AD), which is characterized by progressive decline of cognitive functions, formation of Abeta deposits and neurofibrillary tangles, and loss of neurons. Increased genetic production or direct intracerebral administration of Abeta in animal models results in Abeta deposition, gliosis, and impaired cognitive functions. Whether aging renders the brain prone to Abeta and whether inflammation is required for Abeta-induced learning deficits is unclear. We show that intraventricular infusion of Abeta1-42 results in learning deficits in 9-month-old but not 2.5-month-old mice. Deficits that become detectable 12 weeks after the infusion are associated with a slight reduction in Cu,Zn superoxide dismutase activity but do not correlate with Abeta deposition and are not associated with gliosis. In rats, Abeta infusion induced learning deficits that were detectable 6 months after the infusion. Approximately 20% of the Abeta immunoreactivity in rats was associated with astrocytes. NMR spectrum analysis of the animals cerebrospinal fluid revealed a strong reduction trend in several metabolites in Abeta-infused rats, including lactate and myo-inositol, supporting the idea of dysfunctional astrocytes. Even a subtle increase in brain Abeta1-42 concentration may disrupt normal metabolism of astrocytes, resulting in altered neuronal functions and age-related development of learning deficits independent of Abeta deposition and inflammation.

Aging↗

PubMed2003

Mitochondrial succinic-semialdehyde dehydrogenase of the gamma-aminobutyrate shunt is required to restrict levels of reactive oxygen intermediates in plants.

The gamma-aminobutyrate (GABA) shunt is a metabolic pathway that bypasses two steps of the tricarboxylic acid cycle, and it is present in both prokaryotes and eukaryotes. In plants the pathway is composed of the calcium/calmodulin-regulated cytosolic enzyme glutamate decarboxylase and the mitochondrial enzymes GABA transaminase and succinic-semialdehyde dehydrogenase (SSADH). The activity of the GABA shunt in plants is rapidly enhanced in response to various biotic and abiotic stresses. However the physiological role of this pathway remains obscure. To elucidate its role in plants, we analyzed Arabidopsis T-DNA knockout mutants of SSADH, the ultimate enzyme of the pathway. Four alleles of the ssadh mutation were isolated, and these exhibited a similar phenotype. When exposed to white light (100 micromol of photons per m2 per s), they appear dwarfed with necrotic lesions. Detailed spectrum analysis revealed that UV-B has the most adverse effect on the mutant phenotype, whereas photosynthetic active range light has a very little effect. The ssadh mutants are also sensitive to heat, as they develop necrosis when submitted to such stress. Moreover, both UV and heat cause a rapid increase in the levels of hydrogen peroxide in the ssadh mutants, which is associated with enhanced cell death. Surprisingly, our study also shows that trichomes are hypersensitive to stresses in ssadh mutants. Our work establishes a role for the GABA shunt in preventing the accumulation of reactive oxygen intermediates and cell death, which appears to be essential for plant defense against environmental stress.

Aldehyde Oxidoreductases↗

PubMed2002

Unfolding of quadruplex structure in the G-rich strand of the minisatellite repeat by the binding protein UP1.

The mouse hypervariable minisatellite (MN) Pc-1 consists of tandem repeats of d(GGCAG) and flanked sequences. We have previously demonstrated that single-stranded d(GGCAG)(n) folds into the intramolecular folded-back quadruplex structure under physiological conditions. Because DNA polymerase progression in vitro is blocked at the repeat, the characteristic intramolecular quadruplex structure of the repeat, at least in part, could be responsible for the hypermutable feature of Pc-1 and other MNs with similar repetitive units. On the other hand, we have isolated six MN Pc-1 binding proteins (MNBPs) from nuclear extracts of NIH 3T3 cells. Here, we describe one of those MNBPs, MNBP-B, that binds to the single-stranded d(GGCAG)(n). Amino acid sequences of seven proteolytic peptide fragments of MNBP-B were determined, and the cDNA clones were isolated. MNBP-B was proven identical to the single-stranded DNA-binding protein, UP1. Recombinant UP1 bound to single-stranded d(GGCAG)(n) and other G-rich repetitive sequences, such as d(GTCAGG)(n) and d(GTTAGG)(n). In addition, UP1 was demonstrated by CD spectrum analysis to unfold the intramolecular quadruplex structure of d(GGCAG)(5) and d(TTAGGG)(4) and to abrogate the arrest of DNA synthesis at the d(GGG)(n) site. This ability of UP1 suggests that unfolding of quadruplex DNA is required for DNA synthesis processes.

3T3 Cells↗

PubMed1977

Electron microscopy of fibers and discs of hemoglobin S having sixfold symmetry.

Aggregated forms of deoxyhemoglobin S were examined with a field emission transmission electron microscope. Images of isolated helical fibers were obtained from sickled cell lysates stained directly on the electron microscope grid. Optical and digital analyses of the electron micrographs showed that the fibers are similar to those characterized by J. T. Finch, M. F. Perutz, J. F. Bertles, and J. Döbler [(1973) Proc. Natl. Acad. Sci. USA 70, 718-722] in that they consist of stacked discs each composed of six hemoglobin molecules. The fibers exhibit an outer diameter of 160-170 A and an inner diameter of about 60 A with an axial spacing of 58 A per disc. The fiber can be described as a helix consisting of 56 discs per helical turn. We observed discs of six hemoglobin molecules, which may be stable substructural components of the fibers. They were observed in preparations of hemoglobin fibers and exhibited 6-fold symmetry by power spectrum analysis. A reconstructed image of a disc digitally filtered for 6-fold symmetry has a maximum external diameter of approximately 170 A and a central hole of 60 A diameter and is similar to the axial projection of a single disc from a low-resolution, three-dimensional reconstructed model of a fiber.

Computers↗

PubMed1978

Direct evidence for 6-fold symmetry of the herpesvirus hexon capsomere.

Rotational power spectrum analysis of scanning transmission electron micrographs of negatively stained herpesvirus capsids has given direct evidence for the 6-fold symmetry of the herpesvirus hexon capsomere. Individual hexons have been analyzed in situ without interference from other parts of the capsid because only one level of the capsid was in focus in the micrograph. This study found hexons to have 6-fold symmetry. The majority of the mass of each hexon subunit was seen to lie on a line connecting the centers of adjacent capsomeres. This agrees with analysis of conventional micrographs of capsid fragments, which are also presented, as well as with biochemical data and theoretical expectations.

Microscopy, Electron↗