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At least 1,135 records · Page 63Linked to original sources
PubMed1991

Tissue-specific changes in glutathione and cysteine after buthionine sulfoximine treatment of rats and the potential for artifacts in thiol levels resulting from tissue preparation.

L-Buthionine-S,R-sulfoximine (BSO), a potent inhibitor of gamma-glutamylcysteine synthetase, is commonly used as an experimental tool for the specific depletion of glutathione. Since cysteine is a key precursor for glutathione biosynthesis, we investigated the possibility that BSO might also affect the free cysteine pool in rat liver and kidney tissues in vivo. Male CD(SD)BR rats (150-200 g) were injected ip with various doses of BSO (0.25-4.0 mmol/kg), and glutathione and cysteine were measured in liver and kidney using HPLC with electrochemical detection and/or spectroscopic techniques. No hepatotoxicity or nephrotoxicity was observed at the highest BSO dose (4.0 mmol/kg) used. BSO caused the expected decreases of hepatic and renal glutathione at all doses, although glutathione depletion was more rapid, was achieved at a lower BSO dose, and was more sustained in kidney than in liver. Hepatic cysteine levels nearly doubled 20 min after BSO treatment (1.0 mmol/kg, ip), but were not significantly different from control at later time points. In contrast, renal cysteine was significantly depleted from 20 min to 25 hr postinjection with a time course closely paralleling that of renal glutathione depletion. These changes are discussed in the context of models for inter- and intraorgan transport of glutathione and cysteine. We also provide evidence that an artifact, most likely the gamma-glutamyltranspeptidase (GGT)-initiated breakdown of glutathione, leads to a rapid postmortem increase of cysteine levels in liver and particularly in kidney of rats. Simultaneous decreases in GSH levels can be demonstrated in kidney. This artifact needs to be minimized in toxicological studies of glutathione and cysteine in kidney and other GGT-rich organs, as the measured levels of these thiols may not reflect the true concentrations occurring in vivo.

Animals↗
PubMed1990

Method for recording short latency evoked potentials using an EKG artifact elimination procedure.

This paper describes the application of an EKG elimination procedure, previously reported by the authors, to evoked potentials (EPs) recording using a non-cephalic reference. The method consists of three separate steps: data acquisition, EKG artifact elimination, and EP averaging. EKG artifacts are eliminated from the raw EEG by applying a four step procedure to the simultaneously recorded EEG, EKG and stimulus pulse. The steps are: synchronized partition of the raw EEG, EKG averaging, synchronized repetition, and synchronized subtraction of the EKG estimate from the raw EEG. Average EP values are then obtained by averaging the processed EEG using the stimulus pulse as a trigger. Somatosensory evoked potentials to a hand reference, averaged using the proposed method, were compared with those obtained by two conventional averaging methods, and were shown to be more clearly defined. The advantage of the proposed method for recording short latency EP values with a non-cephalic reference is that it requires fewer sweeps and thus takes less time than other methods. The proposed method may also be applicable to the recording of other EP values.

Adult↗
PubMed1983

A method for long-term artifact-free recording of single unit activity in freely moving, eating and drinking animals.

A method for long-term artifact-free recording of single unit activity in freely moving, eating and drinking animals is described. A dual channel field effect transistor (FET) which functions as dual source followers is mounted directly on the head socket of the animal and the pins are connected directly to chronically implanted microwire electrodes. Unit activity inputs to the FETs from two closely spaced electrode wires, one recording and one indifferent, were differentially amplified through a circuit with high common mode rejection ratio. Use of the FETs reduced the signal source impedance of long lead wires from the electrodes to the main amplifier and differential recording from two close electrodes cancelled mastication-related myoelectric potentials as common mode signals. Both movement and chewing artifacts were completely eliminated by these techniques.

Animals↗
PubMed1985

Artifacts in oral biopsy specimens.

More than proper surgical technique is required to facilitate the proper diagnosis of an oral biopsy specimen. The proper preparation of the tissue for microscopic analysis depends on steps taken by the surgeon, assistant, and histotechnician to reduce the inclusion of artifacts. There are many ways that the exact interpretation of tissue specimens can be compromised. Unfortunately, many practitioners seem to be unaware of the extent of this problem, as well as how easily artifacts can be prevented.

Anesthetics, Local↗
PubMedDate not supplied

Microcomputer analysis of cortical power spectrum: calibration and correlates of behavioral artifacts.

Cortical power spectrum (CPS) is a quantitative estimate of EEG spectral power density. The CPS provides suitably precise data for quantification and statistical inference compared to the qualitative evaluation of EGG when interpreted by clinicians or researchers. In the past decade, the CPS has been applied to the studies of cognitive functions, memory, psi phenomena, speech laterality, and states of consciousness including coma, sleep, anesthesia, pathophysiology and pain state. However, few systematic evaluations of CPS methodology have been reported, rendering cross-laboratory comparisons difficult and external validity of experimental results uncertain. This report first describes a calibration procedure employing a microcomputer system for measuring the functional relationship between input signals and output cortical powers. Second, we examine controlled behavioral artifact effects on the CPS. The behavioral artifacts observed in the CPS can provide a measurement anchor for less ambiguous interpretation of CPS experiments conducted in clinical or laboratory settings.

Cerebral Cortex↗
PubMed1988

Ultrasound artifacts affecting the diagnosis of breast masses.

An investigation of the outcome of over 1600 breast ultrasound examinations revealed a number of scanning artifacts. Artifactual echoes in cysts resulted from inappropriate scanning factors, including focal zone placement, gain, TGC, and gray scale, and from partial volume effect. The absence of a sign suspicious for carcinoma, posterior shadowing to a solid mass, resulted from faulty focal zone placement, or from the mass resting on chest wall tissue. Pathology was sometimes simulated by postsurgical scars, ducts, and benign calcifications. Corrective procedures to alleviate the various scanning artifacts are recommended.

Breast↗
PubMed1994

Renal osteodystrophy and dialysis artifacts as indicators of identification.

Evidence of rare disease may be useful in the identification of unknown remains. Osteodystrophy is a condition commonly associated with chronic renal failure. The presence of renal osteodystrophy and medical artifacts associated with the treatment of kidney failure in human remains may provide information about the individual's medical history. Currently, there are more than 100,000 patients with end stage renal disease in the United States receiving dialysis treatments to replace kidney function, and hundreds of thousands more who have significant chronic kidney failure and are not yet treated with dialysis. Chronic renal failure frequently leads to disorders in the metabolism of vitamin D, calcium, and parathyroid hormone which are extremely difficult to correct. At least three patterns of skeletal change may result: osteitis fibrosa, characterized by increased bone remodelling, increased osteoclastic activity, peritrabecular fibrosis, and a normal mineralization pattern; osteomalacia, with a markedly increased osteoid surface and volume, and impaired mineralization; and mixed osteodystrophy, with increased bone remodelling and moderately impaired mineralization. While these bone changes may not have any clinical manifestations in most patients, they can been seen radiographically and histologically. This evidence may be useful in identifying remains which have been skeletonized, burned, decomposed, or dismembered. Medical artifacts associated with dialysis treatment, such as catheters, polytetrafluoroethylene grafts, and evidence of surgical procedures, are also useful for identification.

Adult↗
PubMedDate not supplied

Simulation of CT reconstruction artifacts associated with multiple-rotation fan-beam data collection.

Artifacts in reconstructed image caused by the errors in projection data depend on the source of the error itself, on the data collection mode and on the reconstruction algorithm. The effect of the multiple-rotation fan-beam data collection modes and corresponding reordered parallel convolution-backprojection algorithms on reconstruction artifacts of this type is analysed.

Humans↗
PubMedDate not supplied

A new software correction approach to volume averaging artifacts in CT.

The nature of artifacts in computed tomography, due to nonlinear partial volume effects, is briefly reviewed. A methodology for correction of these artifacts proposed. This methodology utilizes a correction algorithm for post-processing the original reconstructed CT image. The algorithm utilizes local CT values to predict the probability of volume averaging of bone, air and tissue, and incorporates information from the original image on the spatial extent of the averaging, to correct the nonlinear effects. The algorithm is successfully demonstrated on mathematical phantoms, wherein volume averaging can be introduced over central targets and/or peripheral annuli of tissue, bone, and air. The algorithm is also demonstrated on actual CT brain scans but only for its qualitative effects. It is pointed out that higher order corrections, to be reported in future publications, will further correct the actual clinical scans.

Air↗
PubMed1985

Mascara--an unsuspected cause of magnetic resonance imaging artifact.

It is well recognised that metals, especially iron, will cause artifacts in magnetic resonance (MR) images. Hitherto it has not been recognised that some facial cosmetics contain magnetic materials, in sufficient quantities to cause artifacts. We report a case of a 25-year-old female who had MR images of her orbits made while wearing mascara eye makeup. The resultant images showed distortion of the signal over the anterior aspect of both eyes. Examination following the removal of the eye makeup resulted in the acquisition of normal images. The typical ingredients of mascara are natural and synthetic waxes, glycerine, water, kaolin, preservatives, polymer film formers and pigments. A wide range of pigments may be used, especially iron oxide, which is a constituent of both brown and blue mascara. In addition it is likely that a number of mascaras will be contaminated with heavy metals. As a result of this observation we now ensure that all patients who are undergoing MR imaging of the head, remove all facial cosmetics as well as any jewelry prior to imaging.

Adult↗
PubMedDate not supplied

Fast imaging and other motion artifact reduction schemes: a pictorial overview.

Since 1982, a number of techniques have been introduced for the purpose of reducing motion artifacts in magnetic resonance imaging. These are reviewed with an emphasis on effectiveness and clinical practicality. Physical restraints, data averaging, and gradient moment nulling are widely used at present. Fast imaging techniques, particularly with the advent of saturation pulses (to diminish arterial and venous pulsation artifacts), may be utilized in the future to obtain diagnostic quality abdominal and pelvic images during breath holding.

Abdomen↗
PubMed1990

Contrast manipulation and artifact assessment of 2D and 3D RARE sequences.

The extent of contrast manipulation and the assessment of characteristic artifacts in imaging studies of brain and knee as performed with novel variants of the Rapid Acquisition Relaxation Enhanced (RARE) sequence are reported. Methods of ordering the phase encoding within one or two echo trains are proposed for manipulating T2 contrast. Options for minimizing artifacts associated with the various schemes are discussed. The extent of T1 contrast manipulation in RARE sequences is explored by varying repetition rates in a signal averaging scheme and by applying inversion pulses prior to data acquisition. The results demonstrate that RARE sequences can be utilized for obtaining good quality images with a range of tissue contrast options similar to those associated with slower spin-echo methods. They also suggest that RARE applications need not be confined to highlighting long T2 fluid spaces, an application already well documented.

Adult↗
PubMedDate not supplied

Magnetic field strength dependence of chemical shift artifacts.

The dependence of proton MRI chemical shift artifacts on main magnetic field strength was investigated using three MR whole body systems from 0.3 to 1.5 T with both permanent and superconducting magnet designs. The magnetic field gradients varied from 0.09 to 1.0 gauss/cm. The image bandwidth varied from 8.54 to 32 kHz. Both phantoms and normal volunteers were studied. The chemical shift misregistration error in hertz was determined by the main magnetic field strength of the system which was proportional to the Larmor frequency. The actual image error in millimeters was determined by a combination of the shift in hertz as well as by the amplitude of the magnetic field gradients applied to form the image. Steeper gradients mapped a given shift in hertz onto a smaller millimeter displacement. The higher field strength systems tended to use steeper magnetic field gradients, but this increase was not enough to offset the higher absolute shift in hertz due to the higher Larmor frequencies. In general, the chemical shift in millimeters tended to increase with the increasing field strength despite the steeper imaging gradients. Based on these findings, strategies for minimizing the chemical shift artifact may be developed.

Adipose Tissue↗
PubMed2003

Distinction of bloodstain patterns from fly artifacts.

Forensic scientists may encounter blood spatter at a scene which may be pure or a mixture of fly artifacts and human bloodstains. It is important to be able to make an informed identification, or at least advanced documentation of such stains since the mechanics of production of fly artifacts are not determinable to the crime scene reconstructionist from regular police forces. We describe three cases in which experiments and crime scene reconstruction led to additional information. Case 1: Above the position of a victim, numerous blood stains of the low-high-velocity type were found. Exclusion of these stains being caused by force (but instead caused by the activity of adult blow flies) by use of the following observations that were confirmed in experiments: (a) sperm-/tadpole-like structure with length > width, (b) random directionality, and (c) mixture of round symmetrical and teardrop shaped stains. Case 2: A reddish spatter field was found on a fan chain two rooms away from the place where a dead woman was found. Localization of the spatter on the bottom end of the surface hinted strongly towards fly activity. Case 3: Double homicide; submillimeter stains were found on a lamp between the two corpses. Activity of flies was less likely compared to alternative scenario of moving lampshade and violent stabbing.

Animals↗
PubMed2006

The mammalian fauna associated with an archaic hominin skullcap and later Acheulean artifacts at Elandsfontein, Western Cape Province, South Africa.

The Elandsfontein site, Western Cape Province, South Africa, is well known for an archaic hominin skullcap associated with later Acheulean artifacts. The site has also provided nearly 13,000 mammalian bones that can be identified to skeletal part and taxon. The assemblage derives from 49 species, 15 of which have no historic descendants. Comparisons to radiometrically dated faunas in eastern Africa indicate an age between 1 million and 600 thousand years ago. Unique features of the fauna, including the late occurrence of a dirk-toothed cat and a sivathere, may reflect its geographic origin in a region that was notable historically for its distinctive climate and high degree of biotic endemism. Together, taxonomic composition, geomorphic setting, and pollen extracted from coprolites indicate the proximity of a large marsh or pond, maintained by a higher water table. The small average size of the black-backed jackals implies relatively mild temperatures. The sum of the evidence places bone accumulation during one of the mid-Pleistocene interglacials that were longer and cooler than later ones, including the Holocene. The geomorphic context of the fauna presents no evidence for catastrophe, and most deaths probably resulted from attritional factors that disproportionately killed the young and old. However, only the dental-age profile of long-horned buffalo supports this directly. Field collection methods biased skeletal-part representation, but originally, it probably resembled the pattern in the younger, marsh-edge Acheulean occurrence at Duinefontein 2, 45 km to the south. Excavation there exposed multiple vertebral spreads, which probably mark carcasses from which hominins or large carnivores removed the meatier elements. Bone damage at both sites suggests that, despite abundant artifacts, hominins were much less important than carnivores in the bone accumulation. Together with limited observations from other sites, Elandsfontein and Duinefontein provisionally suggest that Acheulean-age hominins obtained few large mammals, whether by hunting or scavenging.

Animals↗
PubMed2006

Finite pulse width artifact suppression in spin-1 quadrupolar echo spectra by phase cycling.

A phase cycling scheme for suppressing spectral artifacts introduced in quadrupolar echo spectroscopy of spin-1 nuclei due to finite pulse width effects is presented. The phase cycling scheme is developed using the formalism of average Hamiltonian theory and fictitious spin-1 operators. A simulation and experiment on deuterated polyethelene is performed highlighting the spectral artifact introduced by finite pulse widths and successful removal with the proposed phase cycling scheme.

Journal Article↗
PubMed1980

Resistive artifacts in liquid-ion exchanger microelectrode estimates of Na+ activity in epithelial cells.

In experiments on the rabbit urinary bladder epithelium we have identified an electrical artifact in certain liquid ion-sensitive microelectrodes. This artifact arises from the high electrical resistance of the ion-sensitive resins which in some cases are comparable to the resistance of the microelectrode glass wall. For Na+-sensitive microelectrodes this situation led to shunting of the exchanger potential and consequently artifactually high calculations of intracellular Na+ in the rabbit urinary bladder epithelium. A method for minimizing this shunting effect is described. After reduction of the shunt the frequency response of the Na+-sensitive microelectrode was increased and the estimated ai Na+ was decreased to 7 mM.

Animals↗
PubMed2000

Young children's use of functional information to categorize artifacts: three factors that matter.

Three experiments addressed factors that might influence whether or not young children take into account function, as opposed to overall appearance or shape, when they extend the names of novel artifacts. Experiment 1 showed that 4-year-olds more often extend a name on the basis of a demonstrated function when that function provides a plausible causal account of perceptible object structure. Experiment 2 showed that they more often extend a name by function when they respond slowly, and hence thoughtfully. Experiment 3 demonstrated that they are more likely to take function into account when they extend names than when they judge similarities. Comparisons of lexical and non-lexical conditions in younger children failed to show any differences. Overall, the findings suggest that by 4 years of age, children may learn names as labels for novel artifact kinds rather than perceptual classes, and that the processes by which they categorize may be mindful and reflective, as in adults.

Adult↗