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PubMed1998

Renal artery stent implantation in a patient with bilateral renal artery stenoses presenting with flash pulmonary edema.

We describe a patient with a clinical presentation of moderate renal dysfunction, recurrent hospitalizations for congestive heart failure, and an episode of abrupt-onset pulmonary edema (flash pulmonary edema). Diagnostic angiography revealed triple-vessel coronary artery disease (CAD) and bilateral severe renal artery stenosis. This patient underwent successful bilateral renal artery stent implantation with marked improvement in his functional class without further recurrence of pulmonary edema.

Journal Article↗
PubMed1988

Cross-bridge kinetics, cooperativity, and negatively strained cross-bridges in vertebrate smooth muscle. A laser-flash photolysis study.

The effects of laser-flash photolytic release of ATP from caged ATP [P3-1(2-nitrophenyl)ethyladenosine-5'-triphosphate] on stiffness and tension transients were studied in permeabilized guinea pig protal vein smooth muscle. During rigor, induced by removing ATP from the relaxed or contracting muscles, stiffness was greater than in relaxed muscle, and electron microscopy showed cross-bridges attached to actin filaments at an approximately 45 degree angle. In the absence of Ca2+, liberation of ATP (0.1-1 mM) into muscles in rigor caused relaxation, with kinetics indicating cooperative reattachment of some cross-bridges. Inorganic phosphate (Pi; 20 mM) accelerated relaxation. A rapid phase of force development, accompanied by a decline in stiffness and unaffected by 20 mM Pi, was observed upon liberation of ATP in muscles that were released by 0.5-1.0% just before the laser pulse. This force increment observed upon detachment suggests that the cross-bridges can bear a negative tension. The second-order rate constant for detachment of rigor cross-bridges by ATP, in the absence of Ca2+, was estimated to be 0.1-2.5 X 10(5) M-1s-1, which indicates that this reaction is too fast to limit the rate of ATP hydrolysis during physiological contractions. In the presence of Ca2+, force development occurred at a rate (0.4 s-1) similar to that of intact, electrically stimulated tissue. The rate of force development was an order of magnitude faster in muscles that had been thiophosphorylated with ATP gamma S before the photochemical liberation of ATP, which indicates that under physiological conditions, in non-thiophosphorylated muscles, light-chain phosphorylation, rather than intrinsic properties of the actomyosin cross-bridges, limits the rate of force development. The release of micromolar ATP or CTP from caged ATP or caged CTP caused force development of up to 40% of maximal active tension in the absence of Ca2+, consistent with cooperative attachment of cross-bridges. Cooperative reattachment of dephosphorylated cross-bridges may contribute to force maintenance at low energy cost and low cross-bridge cycling rates in smooth muscle.

Actomyosin↗
PubMed1989

Kinetics of contraction initiated by flash photolysis of caged adenosine triphosphate in tonic and phasic smooth muscles.

Laser flash photolysis of caged adenosine triphosphate (ATP), in the presence of Ca2+, was used to examine the time course of isometric force development from rigor states in glycerinated tonic (rabbit trachealis) and phasic (guinea-pig ileum and portal vein) smooth muscles. Photolytic liberation of ATP from caged ATP initiated force development, at 20 degrees C, with half-time (t1/2) of 5.4 s in trachealis and 1.2-2.2 s in the phasic muscles. Prior to photolysis, some muscles were phosphorylated with ATP plus okadaic acid (an inhibitor of myosin light-chain phosphatase) or thiophosphorylated with ATP gamma S to fully activate the regulatory system, before turning on the contractile apparatus. In these prephosphorylated muscles, force development, after caged ATP photolysis, was more rapid than in the unphosphorylated muscles, but the t1/2 values for trachealis (0.8-1.1 s) were still longer than for ileum and portal-vein muscles (0.20-0.25 s). The results suggest that both the contractile machinery and the regulatory system are slower in the tonic than in the phasic smooth muscles. The time course of force development for each muscle type was sigmoidal, with an initial delay (td) of approximately 10% of the t1/2 value. Some possible chemical and mechanical origins of the delay are discussed.

Adenosine Triphosphate↗
PubMed1989

Simple reaction times to lateralized light flashes. Varieties of interhemispheric communication routes.

Simple unimanual reaction times to lateralized light flashes were measured in 40 normal subjects, 4 commissurotomized patients, and a boy with callosal agenesis. In all subjects, reaction times tended to be shorter when the stimuli were presented on the same side as the response hand (uncrossed condition) than on the opposite side (crossed condition). In 2 experiments, the magnitude of the crossed-uncrossed difference (CUD) was greatest in the commissurotimized patients (ranging from 35 to 96 ms), the acallosal boy showed an intermediate CUD (20 and 12 ms for the first and second experiment, respectively), and normal subjects exhibited the smallest CUD (an insignificant 1 ms difference and a significant 3 ms difference in the first and second experiment, respectively). For all subjects, reaction times increased when the stimulus light intensity was decreased (Experiment 1) or when stimulus eccentricity was increased (Experiment 2). However, the effects of these visual parameters on the CUD revealed group and individual differences. Neither stimulus light intensity nor eccentricity affected the CUD in the normals, in 1 of the commissurotomized patients, and in the acallosal boy. The CUDs in these subjects are attributed to the transfer of nonsensory information via the corpus callosum, via ipsilateral corticospinal tracts, and via the anterior commissure or ipsilateral motor pathways, respectively. The CUDs of 2 commissurotomized patients varied with stimulus eccentricity but not intensity. Subcallosal interhemispheric visual transfer is thus apparently more sensitive to stimulus eccentricity than to intensity. The final commissurotomized patient, R.Y., had slower and less accurate responses to stimuli presented in the right visual hemifield during left, but not right, hand responses. An asymmetry in subcortical visual interhemispheric communication is suspected in this patient. The disparate results amongst these subjects are discussed and contrasted with previous findings. Finally, an information processing model of cortical and subcortical interhemispheric communication is presented.

Agenesis of Corpus Callosum↗
PubMed1995

Channels of the corpus callosum. Evidence from simple reaction times to lateralized flashes in the normal and the split brain.

We studied 75 normal subjects and three commissurotomized patients using unimanual simple reaction times to lateralized flashes as a behavioural estimate of interhemispheric transmission time. Three different versions of the paradigm were performed: (i) the basic task; (ii) a motor task, with an increased complexity of the motor response; and (iii) a visual task, with an increased complexity of the visual stimulus presentation. We tested two hypotheses. First, that the new versions of the simple reaction time task result in shifts in hemispheric specialization for processing motor output (indicated by a main effect of response hand) or visual input (indicated by a main effect of visual field) alone, without affecting callosal transmission. In that case normals and split brain patients would show no significant task by response hand by visual field interaction and no significant task by crossed-uncrossed difference interaction. Secondly, that the new versions of the task affect callosal transfer. In that case, normals, but not split brain patients, would show a significant task by response hand by visual field interaction and a significant task by crossed-uncrossed difference interaction. Results are consistent with the latter hypothesis, showing that the motor task significantly changed the response hand by visual field interaction and the crossed-uncrossed difference, but only in normal subjects, perhaps producing a switch in the callosal channel subserving the interhemispheric transfer.

Adult↗
PubMedDate not supplied

Flash alkylation for the identification of barbiturates in biological material.

The gas chromatographic identification of barbiturates isolated from biological material is not optimal, and due to their polar nature, it is difficult to obtain good resolution on most columns. To improve resolution, flash alkylation appeared to be a reasonable alternative. Methyl, ethyl, and butyl derivatives were prepared for various drugs found in the "acid-neutral" extract and the Kovats retention indices (Ir) were determined on SE-30, OV-17, and SP-2250. The Ir of the alkylated derivatives of the barbiturates are highly reproducible. One column and two alkylated derivatives can be used for the qualitative analysis of barbiturates in extracts of biological material, even when the Stas-Otto extract is used.

Alkylation↗
PubMed1985

First clinical results with digital flashing tomosynthesis in coronary angiography.

Digital flashing tomosynthesis (D-FTS) investigations have been performed using a new nonlinear reconstruction algorithm. It is called extreme-value decoding and produces significantly less artefact than back projection used commonly in tomosynthesis. The reduction of artefact allows the use of tomosynthesis based on only four projections in the case of dilute objects, i.e. objects with only a small number of high absorbing voxels. This condition can be realized in angiography by cancelling soft-tissue and bones by subtraction (e.g. DSA technique). The new technique has been carried out in 10 patients with coronary artery disease after investigation with standard 35 mm cineangiography. For the recording step of the D-FTS images we have used a multiple X-ray source. For the digital nonlinear reconstruction step we have used a VAX 11/780 computer. The estimated degree of stenosis found by D-FTS tomograms shows good accordance with the cineangiographic studies. The amount of contrast medium, the X-ray dose, and the investigation time are significantly reduced, because D-FTS requires only a single pre- and post-injection multiple perspective-image for each coronary artery.

Cineangiography↗
PubMed1990

X-ray diffraction and flash photolysis studies of M intermediate of lattice-contracted purple membrane.

The effects of cross-linking and lattice contraction of purple membrane (PM) on the photodynamics of bacteriorhodopsin (bR) and on the tertiary structure were studied by flash photolysis and X-ray diffraction. To get a contracted lattice form of PM, native PM, and/or PM cross-linked by glutaraldehyde were treated with deoxycholate or Triton X-100. Part of the Triton-treated cross-linked PM was further incubated with Bio-Beads SM-2 to remove Triton X-100. In the modified PM, several long-lived components of the M intermediate appeared, the features of which were related to the environment of bR. Also, X-ray diffraction studies using synchrotron radiation were performed on the modified PM under intense light irradiation (lambda greater than 500 nm) in which 40-80% of bR was photoconverted to the M state. In the Triton-treated cross-linked PM dispersed in 0.25% Triton X-100, the unit cell of membrane crystalline lattice was enlarged from 58.8 to 59.8 A and the crystalline order decreased with irradiation. The analysis of X-ray diffraction patterns suggests that light-induced conformational changes of bR correlated with the Triton content of the environment and an increase of substitution disorder was caused by these changes, but the average location of bR was unchanged. However, the other modified PM showed no significant changes of diffraction, upon light irradiation.

Absorption↗
PubMed2003

Disassociation of carbon disulfide-induced depression of flash-evoked potential peak N166 amplitude and norepinephrine levels.

Exposure to organic solvents frequently causes functional impairment of the central nervous system (CNS). One method to examine the effects of solvent exposure on visual function is flash-evoked potentials (FEPs). Greater knowledge of the role of various neurotransmitters in generating FEP peaks would be beneficial for understanding the basis of neurotoxicant-induced changes. FEP peak N166 is influenced by the psychological construct of arousal, which in turn is believed to be influenced by the function of neurons containing norepinephrine (NE). Because of its known effects on both NE and FEPs, we utilized carbon disulfide (CS2) as a means to examine the possible role of NE in modulating the amplitude of FEP peaks N36 and N166. Our hypothesis was that CS2-induced alterations in cortical NE levels would be correlated with changes in FEP peak N36 and N166 amplitudes. Adult male Long-Evans rats were implanted with electrodes over their visual cortex and allowed to recover. To develop peak N166, FEPs were recorded for two days prior to dosing. On the third day, FEPs were recorded prior to dosing, and one group of animals was sacrificed to serve as pretreatment controls. The remaining animals were dosed ip with 0 (corn oil vehicle; 2 ml/kg), 100, 200, or 400 mg/kg CS2. The treated animals were retested at 1, 4, 8, or 24 h after dosing, immediately sacrificed, and samples of the cortex, cerebellum, striatum, and brain stem were frozen for high performance liquid chromatography (HPLC) analysis of monoamine levels. Treatment with CS2 decreased peak N166 amplitude at 1 h, and peak N36 amplitude was depressed at 4 h, relative to the subject's pretreatment values. Peak latencies were increased, and colonic temperature was decreased by treatment with CS2. Exposure to CS2 depressed NE levels in the cortex, brain stem, and cerebellum 4 h after treatment. Conversely, at 4 h, levels of dopamine (DA) and its metabolite 3,4-dihydroxyphenylacetic acid were increased in the brain stem and cerebellum, and levels of the DA metabolite homovanillic acid were increased in the brain stem. Levels of serotonin were unaffected by CS2 treatment. There was a slight increase in striatal levels of the serotonin metabolite 5-hydroxyindole acetic acid at all times after treatment with CS2. There was no apparent association between the decreases in NE levels and the reductions in amplitudes for peaks N36 and N166. The neurochemical mechanism for CS2-induced reductions in FEP peak amplitudes remains to be determined.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1989

Intraoperative flash fires associated with disposable cautery.

Three cases of intraoperative flash fires associated with the use of disposable thermal cautery units are described. As opposed to similar reports in the literature, two of the three cases were not associated with an elevated oxygen concentration at the operative site. Precautions in the use of these units or the use of mono- or bipolar cautery units are recommended.

Aged↗
PubMed1990

Monitoring of flash visual evoked potentials during neurosurgical operations.

In summary, our results suggest that flash VEP monitoring is not specific for visual acuity and has not proved helpful as an intraoperative warning system. The future challenge will be to devise a method which activates only those fibers specific to visual acuity and which provides reproducible and reliable information quickly enough that adjustments in patient management can be made.

Anesthesia, General↗
PubMed1990

Surface coil FLASH magnetic resonance imaging of the fasting and secretin-stimulated pancreas.

The purpose of this study is to investigate the response of the pancreas to secretin stimulation using magnetic resonance imaging (MRI). Using the Siemens 1.0 T Magnetom and a Helmholtz surface coil, single breath FLASH-MRI of the normal fasting pancreas was performed in the prone position, both before and after a 20-minute period after intravenous (IV) bolus injection of secretin (2 cu/kg). T2*-weighted fast low-angle shot sequences (TR = 150 mseconds; TE = 30 mseconds; flip angle = 10 degrees; matrix = 256 X 256; acquisitions = 2) demonstrated an immediate response manifested by a significant distension of the duodenum with fluid secreted by the pancreas, as well as a gradual decline of the pancreas/muscle signal intensity (SI) ratio over time. Twenty minutes after secretin administration, the mean percent decrease of the pancreas/muscle SI ratio in six volunteers was 11.6 +/- 6.4 (1-STD). This is statistically significant (P less than .003) given a mean percent increase of the pancreas/muscle SI ratio of 1.6 +/- 4.8 (1-STD) in five volunteers 20 minutes after bolus injection of saline (control). Although significant duodenal distension is easily demonstrated after secretin administration, the decrease of the relative pancreatic SI over time is visually subtle. Further work is needed to enhance imaging of the physiologic response of the pancreas using even more rapid imaging techniques.

Adult↗
PubMedDate not supplied

Cerebral blood volume maps with dynamic contrast-enhanced T1-weighted FLASH imaging: normal values and preliminary clinical results.

PURPOSE: In this article we investigate the application of a method that uses the relaxation effect of bolus-like injected Gd-DTPA to quantify regional cerebral blood volume (rCBV). The aim of the study was to determine if the method provides correct rCBV values in healthy subjects as well as to obtain additional diagnostic information for patients with a glioma or stroke. METHOD: Twenty healthy subjects, 12 patients with brain infarctions, and 18 patients with gliomas were examined. A series of 64 sequential images of one slice was recorded during bolus transit with a FLASH sequence. The measured signal intensity-time curves were converted pixel-wise to concentration-time curves from which the rCBV images were calculated applying the indicator dilution method. RESULTS: An average value for gray and white matter of 4.4 +/- 1.6 vol% was obtained for the group of healthy subjects. The grading of the tumors could be classified according to the differences of their corresponding rCBV values. Fifty percent of the infarct patients had to be excluded from the analysis in the acute phase due to mispositioning of the slice and data degradation by gross motion artifact. Different rCBV values were found for areas that develop later into gliotic scars or cystic necrosis. CONCLUSION: The proposed method is easy to apply in clinical routine MR investigations and provides valuable information for noninvasive, preoperative assessment of tumor grading. It can also provide additional criteria for estimating the histological outcome and with it the degree of ischemia in stroke patients.

Adolescent↗
PubMed1993

Effects of hypertonic and isotonic fluid infusion on the flash evoked potential in rats: hemorrhage, resuscitation, and hypernatremia.

In resuscitation from hemorrhagic shock, very small volumes of hypertonic saline (HS) improve blood pressure while reducing intracranial pressure and edema formation. The effects of hypertonic resuscitation fluids and hypernatremia on electrophysiologic brain function have not been studied. The present study was done in two parts. First we examined the effects of hemorrhagic shock and resuscitation with either 7.5% HS or lactated Ringer's (LR) solution on the flash evoked potential (FEP). Rats were bled to a mean arterial pressure (MAP) of 35 mm Hg for 1 hour, then resuscitated with HS (n = 10) or LR (n = 10) to a MAP of 80 mm Hg for another hour. Resuscitation required 3.8 +/- 0.5 mL/kg HS and 42.9 +/- 7.5 mL/kg LR (p < 0.05). During hemorrhage, FEP latencies increased and amplitudes decreased. During resuscitation, these variables returned toward baseline values. There were no significant differences between groups, although HS tended to restore the FEP better than LR. We next examined the effects on the FEP of hypernatremia and hyperosmolarity produced by two different hyperosmotic fluids. Over a 1-hour period, 16 mL/kg HS (n = 8), 16 mL/kg IsoSal (4.5% saline, 5.9% glucose, 6.4% mixed amino acids; n = 8), or 40 mL/kg LR (n = 8) was infused into normovolemic rats. Plasma sodium levels increased in both hyperosmotic groups (baseline = 145.2 +/- 0.7 mEq/L; after infusion, HS = 202.4 +/- 9.8 mEq/L, IsoSal = 163.3 +/- 4.2 mEq/L; p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1977

Reaction time to scotopic flashes of light.

Reaction time (RT) to scotopic flashes of light presented at various locations along the horizontal meridian near the fovea was measured. RT progressively decreased from a maximum near the fovea to a near-asymptotic value at an eccentricity of 12 deg in both the nasal and the temporal retina.

Adult↗
PubMed1985

Flicker electroretinograms and visual evoked potentials in the evaluation of laser flash effects.

Electroretinograms (ERG's) and visual evoked potentials (VEP's) were recorded from four cynomolgus monkeys in response to a sinusoidally flickering argon laser beam (514 nm) producing a 50-micron spot on the fovea. Super-position of a 20-Hz train of six pulses of Q-switched (120 ns) frequency-doubled neodymium laser light (532 nm) at "safe" exposure energies in 250 ms had no significant effects on the ERG (p greater than 0.05). The VEP was disrupted significantly (p less than 0.001) but demonstrated recovery within 500 ms of the initial pulse. Therefore, flash effects of pulsed visible lasers at these doses on suprathreshold luminance processing are probably limited only to the exposure period.

Animals↗
PubMed1988

Laser silicone flash.

Use of the CO2 laser to remove breast siliconosis is described. The flash accompanying this use of the laser is described, and a photograph is submitted to document this previously undescribed phenomenon.

Adult↗