2-minute Exposure Research Articles

Fast and furious: successful survival and resumption of meiosis in immature human oocytes vitrified and warmed using a short protocol

RESEARCH QUESTIONCan immature oocytes vitrified and warmed using a short protocol survive and resume meiosis? DESIGNThis study examined modifications of oocyte vitrification and warming protocols that shorten the time of exposure to vitrification and warming solutions. A total of 561 germinal vesicles (GV), and 218 metaphase I (MI) oocytes that were immature at oocyte retrieval were vitrified at room temperature in 2 minutes. Warming was done at 37°C in 2 minutes. Resumption of meiotic activity was evaluated after 24 and 48 hours of culture. Two different commercially available vitrification and warming kits were used for comparison. RESULTSNinety five percent of GV oocytes survived with no difference observed between kits. The survival of MI oocytes was on average 95.4% and not significantly different between the two kits. Of the 533 GV that survived, 491 converted to MI (92.1%). After culture for 48 hours, 54.4% converted to MII oocytes. In addition, of the 208 MI that survived the warming, 84.1% converted to MII oocytes after culture for 24 hours. CONCLUSIONSVitrification and warming of oocytes at different nuclear maturation stages can be done with a 2-minute exposure time to hypertonic and a 2-minute exposure time to hypotonic solutions. With this approach, the oocytes are less exposed to room temperature during dehydration and rehydration. Warming in 0.5M sucrose helps to maintain and support the potential to resume nuclear meiotic activity of oocytes and conversion from GV to MI and to MII oocytes.

EVALUATION OF THE STEREOSCOPIC DOSE DISTRIBUTION IN ENDOSCOPIC RETROGRADE CHOLANGIOPANCREATOGRAPHY ROOM USING N1 PHANTOM AND TLD TECHNIQUE

This study envisaged the evaluation of the stereoscopic dose distribution and the corresponding exposure dose for the medical staff in endoscopic retrograde cholangiopancreatography (ERCP) room using the spatial dose distribution method and thermo-luminescent dosimetry (TLD) technique. Feasibility screening and calibration of 135 new TLD-100H chips were performed and sealed into 45 packages with 3 TLDs per pack. Subsequently, the 45 TLD packs were allocated in a matrix form in the ERCP room ([Formula: see text][Formula: see text]cm2) with various heights of 85, 90, 130, 150, and 180[Formula: see text]cm above the ground. In addition, three human-sized dolls with lead vast were located at the position of the medical staff to simulate the ambient exposure dose. The TLDs were held for 2-minute exposure (max, min, average) [Formula: see text] Gy dose as 85[Formula: see text]cm (520.9, 14.9, 31.1), 90[Formula: see text]cm (428.6, 15.7, 28.6), 130[Formula: see text]cm (40.7, NA, 28.0), 150[Formula: see text]cm (1650.3, NA, 1650.3) and 180[Formula: see text]cm (17.6, 15.0, 16.4), respectively. The minimum detectable limit (MDL) of the TLD chips was 6.85[Formula: see text]nC, and the TLD dose calibration curve was revised by using a weighting factor according to lean backward scenario to reach low interception. It was found that the maximal exposure dose of the annual workload (12[Formula: see text]m/d*5[Formula: see text]d/wk*50[Formula: see text]wk/yr=3000[Formula: see text]m) was overestimated as 14.7, 14.5, and 14.1[Formula: see text]mGy, respectively for the medical doctors, radiologists and nurses from the viewpoint of health physics.

Building the Evryscope: Hardware Design and Performance

The Evryscope is a telescope array designed to open a new parameter space in optical astronomy, detecting short-timescale events across extremely large sky areas simultaneously. The system consists of a 780 MPix 22-camera array with an 8150 sq. deg. field of view, 13″ per pixel sampling, and the ability to detect objects down to in each 2-minute dark-sky exposure. The Evryscope, covering 18,400 sq. deg. with hours of high-cadence exposure time each night, is designed to find the rare events that require all-sky monitoring, including transiting exoplanets around exotic stars like white dwarfs and hot subdwarfs, stellar activity of all types within our galaxy, nearby supernovae, and other transient events such as gamma-ray bursts and gravitational-wave electromagnetic counterparts. The system averages 5000 images per night with ∼300,000 sources per image, and to date has taken over 3.0M images, totaling 250 TB of raw data. The resulting light curve database has light curves for 9.3M targets, averaging 32,600 epochs per target through 2018. This paper summarizes the hardware and performance of the Evryscope, including the lessons learned during telescope design, electronics design, a procedure for the precision polar alignment of mounts for Evryscope-like systems, robotic control and operations, and safety and performance-optimization systems. We measure the on-sky performance of the Evryscope, discuss its data analysis pipelines, and present some example variable star and eclipsing binary discoveries from the telescope. We also discuss new discoveries of very rare objects including two hot subdwarf eclipsing binaries with late M-dwarf secondaries (HW Vir systems), two white dwarf/hot subdwarf short-period binaries, and four hot subdwarf reflection binaries. We conclude with the status of our transit surveys, M-dwarf flare survey, and transient detection.

Pupillary Responses to Full-Field Chromatic Stimuli Are Reduced in Patients with Early-Stage Primary Open-Angle Glaucoma

To evaluate the ability of chromatic pupillometry to reveal abnormal pupillary responses to light in patients with early-stage primary open-angle glaucoma (POAG) and to test whether the degree of pupillometric impairment correlates with structural hallmarks of optic nerve damage in the disease. Cross-sectional study. Forty-six patients with early-stage POAG (63.4±8.3 years, 63% male, 87% ethnic-Chinese) and 90 age-matched healthy controls (61.4±8.6 years, 34% male, 89% ethnic-Chinese). Patients with POAG had a visual field mean deviation (VFMD) of-6 decibels or better on automated perimetry. Each participant underwent a monocular 2-minute exposure to blue light (462 nm) followed by another 2-minute exposure to red light (638 nm) using a modified Ganzfeld dome equipped with a light-emitting diode lighting system. The light stimuli intensity was increased logarithmically to evaluate the combined extrinsic and intrinsic response of intrinsically photosensitive retinal ganglion cells (ipRGCs). Light-induced changes in horizontal pupil diameter were assessed monocularly using infrared pupillography. Baseline-adjusted, light-induced pupillary constriction amplitudes were calculated, and individual irradiance-response curves were constructed for each stimulus. Pupillary constriction amplitudes were compared between groups and across light intensities using a linear mixed model analysis. The linear relationship between pupillometric parameters and different structural and functional features of glaucoma was assessed using Pearson's correlation analysis. Light-induced pupillary constriction was reduced in patients with early-stage POAG compared with controls at moderate to high irradiances (≥11 Log photons/cm2/s) of blue (P= 0.003) and red (P < 0.001) light. Maximal pupillary constriction amplitude was correlated with retinal nerve fiber layer thickness (RNFL) thickness (blue: r= 0.51, P < 0.001; red: r= 0.45, P= 0.002) in patients with POAG but not in controls. Conversely, pupillometric parameters were not correlated with visual field scores in patients with early-stage POAG. Patients with early-stage POAG exhibit reduced pupillary responses to moderate and high irradiances of blue and red lights. This wavelength-independent functional alteration correlates with structural thinning of the RNFL and could be the consequence of dysfunction or loss of melanopsin expressing ipRGCs in the early stages of the disease.

Evryscope Science: Exploring the Potential of All-Sky Gigapixel-Scale Telescopes

Low-cost mass-produced sensors and optics have recently made it feasible to build telescope arrays which observe the entire accessible sky simultaneously. In this article, we discuss the scientific motivation for these telescopes, including exoplanets, stellar variability, and extragalactic transients. To provide a concrete example we detail the goals and expectations for the Evryscope, an under-construction 780 MPix telescope which covers 8660 sq. deg. in each 2-minute exposure; each night, 18,400 sq. deg. will be continuously observed for an average of ≈6 hr. Despite its small 61 mm aperture, the system’s large field of view provides an étendue which is ∼10% of LSST. The Evryscope, which places 27 separate individual telescopes into a common mount which tracks the entire accessible sky with only one moving part, will return 1%-precision, many-year-length, high-cadence light curves for every accessible star brighter than ∼16th magnitude. The camera readout times are short enough to provide near-continuous observing, with a 97% survey time efficiency. The array telescope will be capable of detecting transiting exoplanets around every solar-type star brighter than mV = 12, providing at least few-millimagnitude photometric precision in long-term light curves. It will be capable of searching for transiting giant planets around the brightest and most nearby stars, where the planets are much easier to characterize; it will also search for small planets nearby M-dwarfs, for planetary occultations of white dwarfs, and will perform comprehensive nearby microlensing and eclipse-timing searches for exoplanets inaccessible to other planet-finding methods. The Evryscope will also provide comprehensive monitoring of outbursting young stars, white dwarf activity, and stellar activity of all types, along with finding a large sample of very-long-period M-dwarf eclipsing binaries. When relatively rare transients events occur, such as gamma-ray bursts (GRBs), nearby supernovae, or even gravitational wave detections from the Advanced LIGO/Virgo network, the array will return minute-by-minute light curves without needing pointing toward the event as it occurs. By coadding images, the system will reach V ∼ 19 in 1-hr integrations, enabling the monitoring of faint objects. Finally, by recording all data, the Evryscope will be able to provide pre-event imaging at 2-minute cadence for bright transients and variable objects, enabling the first high-cadence searches for optical variability before, during and after all-sky events.

Impedance-stabilized positive corona discharge and its decontamination properties

The point-to-plane DC corona discharge in air at atmospheric pressure was stabilized by a serially connected ballast impedance. The ballast impedance was implemented by a resistor-capacitor group connected in parallel. In the case of connecting the serial impedance into the electric circuit of a negative corona, the transition into a spark takes place at parameters similar to those of a non-stabilized discharge. In contrast, in the case of a positive corona, the discharge does not undergo a transition into a spark, but rather into a mode of periodic streamers. We measured the bactericidal effect of the stabilized discharge. The experiments showed that after a 2-minute exposure the quantity of surviving bacteria decreased from 95% for a non-stabilized discharge down to 5% for a stabilized one.

154 SENSORY BIAS PREDICTS POSTURAL STABILITY, ANXIETY, AND COGNITIVE PERFORMANCE IN HEALTHY ADULTS WALKING IN NOVEL DISCORDANT CONDITIONS

We designed a gait training study that presented combinations of visual flow and support surface manipulations to investigate the response of healthy adults to novel discordant sensorimotor conditions. We aimed to determine whether a relationship existed between subjects visual dependence and their scores on a collective measure of anxiety, cognition, and postural stability in a new discordant environment presented at the conclusion of training (Transfer Test). A treadmill was mounted to a motion base platform positioned 2 m behind a large visual screen. Training consisted of three walking sessions, each within a week of the previous visit, that presented four 5-minute exposures to various combinations of support surface and visual scene manipulations, all lateral sinusoids. The conditions were scene translation only, support surface translation only, simultaneous scene and support surface translations in-phase, and simultaneous scene and support surface translations 180 out-of-phase. During the Transfer Test, the trained participants received a 2-minute novel exposure. A visual sinusoidal roll perturbation, with twice the original flow rate, was superimposed on a sinusoidal support surface roll perturbation that was 90 out of phase with the scene. A high correlation existed between normalized torso translation, measured in the scene-only condition at the first visit, and a combined measure of normalized heart rate, stride frequency, and reaction time at the transfer test. Results suggest that visually dependent participants experience decreased postural stability, increased anxiety, and increased reaction times compared to their less visually dependent counterparts when negotiating novel discordant conditions.

Cellular effects of mitomycin-C on human corneas after photorefractive keratectomy

To investigate the effects of mitomycin-C (MMC) on epithelial and keratocyte cell kinetics after photorefractive keratectomy (PRK) using an in vitro human cornea model. Department of Academic Ophthalmology, Rayne Institute, St. Thomas' Hospital, London, United Kingdom. Twenty-four human eye-bank corneas were placed in a specially designed acrylic corneal holder and cultured using the air-interface organ culture technique for up to 4 weeks. The corneas were divided into 3 groups. Group 1 consisted of 8 human corneas that had -9.00 diopter (D) myopic PRK without MMC application. Group 2 consisted of 8 corneas that had -9.00 D PRK with MMC (0.2 microg/mL) application for 1 minute on the stromal surface after ablation. Group 3 consisted of 8 corneas that had -9.00 D PRK with 2-minute exposure to MMC (0.2 microg/mL). Temporal events in epithelial and keratocyte cell kinetics were evaluated using digital imaging, confocal microscopy, and light microscopy. Epithelial latency was significantly delayed with MMC application in Groups 2 and 3 (P<.001). Epithelial migration was delayed in Group 3 (2-minute exposure) compared to migration in Group 2 (P<.04), with a consequent delay in epithelial closure (P<.001). Group 3 corneas had poorly differentiated epithelium that was significantly thinner than in Groups 1 and 2 (P<.0001). A significant delay in keratocyte regeneration occurred after MMC application (P<.0005). At 4 weeks, the anterior stromal cell density was significantly lower in Group 3 than Group 2 (P<.001). There were no significant differences in the mid- and posterior stromal keratocyte density between the groups. Results suggest that epithelial healing after MMC is characterized by prolonged latency and decreased migration rate dependent on exposure time. Mitomycin C application did not result in increased loss of keratocytes, but it significantly delayed keratocyte repopulation in the anterior stroma. The use of MMC 0.2 microg/mL for 1 minute resulted in optimum modulation of healing characterized by reduced keratocyte activation with normal epithelial differentiation.

Pigeon-frequented areas, garbage piles and dog faeces as possible sources of Candida and Cryptococcus infections for humans and animals.

A study was carried out to establish the presence of Cryptococcus neoformans and Candida species in two pigeon-frequented areas; garbage piles from two separate sites in Nairobi, and dog faeces from Small animal clinic, University of Nairobi, Kabete. The sampling included both solid materials and air. Potato Dextrose agar, CHROMagar and urea media were used for isolation and characterization of these yeasts. Various species of Candida and Cryptococcus neoformans were isolated in numbers ranging from 104 to 105 colony forming units per gramme or per 2-minute exposure to air; from both pigeon-frequented areas and garbage sites. Cryptococcus was isolated more than Candida species in pigeon-frequented areas, while the reverse was the case for garbage sites, both for solid and aerial samples. The dog faeces yielded Candida organisms mainly. The presence of these yeasts in both solid samples and air highlights the possibility of these areas, which are frequently traversed by humans and animals (including chickens and other birds), as being possible sources of infection for humans and animals. Aerial contamination means the organisms can be disseminated far and wide easily. The Kenya Veterinarian Vol. 29 2005: pp. 18-20

Hydrogen peroxide decreases pHi in human aortic endothelial cells by inhibiting Na+/H+ exchange.

Postischemic endothelial dysfunction may occur as a result of the effects of endogenous oxidants like hydrogen peroxide. Since endothelium-dependent vasodilator function may be affected by pHi, the effect of hydrogen peroxide on endothelial pHi was examined. Hydrogen peroxide (100 micromol/L for 10 minutes) decreased pHi from 7.24+/-0.01 to 7.02+/-0.02 and inhibited recovery from an ammonium chloride-induced intracellular acid load in carboxy SNARF 1 (c-SNARF 1)-loaded human aortic endothelial cells in bicarbonate-free solution. Prior inhibition of Na+/H+ exchange with 5-(N-ethyl-N-isopropyl)amiloride (10 micromol/L), by removal of extracellular Na+, or by glycolytic inhibition with iodoacetic acid blocked the subsequent effect of hydrogen peroxide on pHi. A 2-minute exposure to 100 micromol/L H2O2 decreased intracellular ATP levels by approximately 40%; this was prevented by 3-aminobenzamide and nicotinamide (1 mmol/L each), inhibitors of the DNA repair enzyme poly(ADP-ribose) polymerase. Both 3-aminobenzamide and nicotinamide significantly inhibited the hydrogen peroxide-induced intracellular acidification and the effect of hydrogen peroxide on recovery from an intracellular acid load. Hydrogen peroxide decreases pHi in human endothelial cells by inhibiting Na+/H+ exchange. This appears to be mediated by activation of the DNA repair enzyme poly(ADP-ribose) polymerase and subsequent depletion of intracellular ATP. Since a decrease in pHi in this range may alter the activity of NO synthase or affect the synthesis of vasodilator prostaglandins, the effect of hydrogen peroxide on the endothelial Na+/H+ exchanger may be important in the pathogenesis of postischemic endothelial dysfunction.

A cellular mechanism contributing to postvagal tachycardia studied in isolated pacemaker cells from cat right atrium.

Vagal nerve-induced inhibition of the heartbeat is followed by a postvagal increase in heart rate above control levels, postvagal tachycardia. In the present study, we used a perforated-patch/whole-cell recording method to determine the role of L-type Ca2+ current (ICa,L) and the hyperpolarization-activated inward current (I(f)) in the positive chronotropic response elicited by withdrawal of acetylcholine (ACh). Experiments were performed on sinoatrial node (SAN) and latent atrial pacemaker (LAP) cells isolated from cat right atrium. Withdrawal of a 2-minute exposure to 1 mumol/L ACh elicited a rebound stimulation of ICa,L in both SAN (33 +/- 4%) and LAP (50 +/- 6%) cells above control. Similarly, withdrawal of ACh (1 mumol/L) elicited a rebound stimulation of I(f) in both SAN (21 +/- 4%) and LAP (20 +/- 6%) cells. During the rebound stimulation of ICa,L, peak amplitude was increased throughout the voltage range, and the voltage dependence of activation was shifted to more negative voltages. Action potential recordings from both SAN and LAP cells showed that following ACh-induced inhibition, withdrawal of ACh elicited a concomitant rebound increase in action potential amplitude ( + 21 +/- 2% and + 21 +/- 3%, respectively) and decrease in pacemaker cycle length (30 +/- 5% and 44 +/- 5%, respectively) compared with control. H-89 (2 mumol/L), an inhibitor of cAMP-dependent protein kinase A, abolished the rebound increase of ICa,L, I(f), action potential amplitude, and decrease in pacemaker cycle length elicited by withdrawal of ACh. In the presence of 2 mmol/L cesium, a blocker of I(f), the rebound decrease in pacemaker cycle length elicited by withdrawal of ACh was unchanged. We conclude that in SAN and LAP cells, withdrawal of ACh elicits a positive chronotropic response primarily through a cAMP-mediated rebound stimulation of ICa,L. These findings are the first demonstration of an intrinsic cellular mechanism that may contribute directly to the nonadrenergic component of postvagal tachycardia.

Endocytosis and uptake of lucifer yellow by cultured atrial myocytes and isolated intact atria from adult rats. Regulation and subcellular localization.

The time course of endocytic uptake of Lucifer yellow (LY) was followed by fluorescence and electron microscopy after exposure of primary cultures of atrial myocytes from adult rats to LY under conditions that prevented transplasmalemmal LY entry via channels or carriers. After a 2-minute exposure to LY at 37 degrees C, electron microscopy revealed classic clathrin-coated vesicles fused to endosomes, which were absent in LY-free medium or at 2 degrees C, suggesting that LY turns on endocytosis or accelerates a slow constitutive endocytosis. Fluorescence microscopy, which detected no LY entry at 2 minutes in LY, showed punctate cytoplasmic fluorescent densities after 10 minutes, which were readily distinguishable from intrinsic perinuclear fluorescence. Fluorescence microscopy after immunostaining with antibodies against clathrin, vacuolar H(+)-ATPase, atrial peptide, or a marker for acidified compartments suggested LY sorting into an acidified prelysosomal pathway. Using absence of punctate fluorescence after 10 minutes in LY as a criterion for inhibition of endocytosis, we showed that endocytosis was inhibited by inhibitors of protein phosphatases 1 and 2A or inhibitors of cAMP-dependent protein kinases 1 and 2, by effects of caffeine on sarcoplasmic reticulum Ca2+ release, and by temperatures below 18 degrees C, but not by staurosporine, phorbol esters, pertussis toxin, thapsigargin, preventing contractions with nifedipine, ryanodine and low [Ca2+]o, or raising cytosolic cAMP concentrations. Both phosphatase inhibitors and caffeine also inhibited a fraction of LY uptake by intact rat atria. We conclude that endocytic uptake of LY is an energy-dependent, specifically regulated process, whose understanding and control are potentially important for the medically relevant problem of introducing drugs and macromolecules into atrial heart muscle cells.

The mucoid cap over superficial gastric damage in the rat: A high-pH microenvironment dissipated by nonsteroidal antiinflammatory drugs and endothelin

The ability of the “mucoid cap” of mucus, fibrin, and cellular debris that forms over sites of superficial gastric damage to provide a relatively high-pH microenvironment was investigated in the rat. Furthermore, the effects of administration of nonsteroidal antiinflammatory drugs or reduction of mucosal blood flow on this microenvironment were investigated. Superficial mucosal damage induced by a 2-minute exposure to Hypertonic saline produces a mucoid cap that has a pH of 4–6 despite the presence in the lumen of a solution of acid with a pH of less than 1. This relatively high-pH microenvironment remained even when the exposure to 0.15-mol/L HCl was continued for as long as 1 hour. Intraperitoneal administration of indomethacin (5 mg/kg) or naproxen (10 mg/kg) resulted, within 10–25 minutes, in complete dissipation of this high-pH microenvironment, with the subsequent development of hemorrhagic erosions. These effects of indomethacin and naproxen occurred subsequent to significant inhibition of gastric prostaglandin synthesis by these agents. Rapid dissipation of the pH gradient could also be produced by brief (30-second) clamping of the arterial blood supply to the chambered mucosa or by systemic administration of a vasoconstrictor (endothelin-1), in both cases resulting in the development of hemorrhagic erosions. These results show that the mucoid cap over sites of superficial damage provides a relatively high-pH microenvironment and that dissipation of this microenvironment by inhibitors of prostaglandin synthesis or by reduction of mucosal blood flow can convert sites of superficial mucosal injury to hemorrhagic erosions. Such inhibitory effects might contribute to the ulcerogenic actions of nonsteroidal antiinflammatory drugs.

Effects of ultrasound on the corneal endothelium: II. The endothelial repair process.

The responses of corneal endothelium to a 2-minute exposure of ultrasound from a clinical phacoemulsification device have been studied by specular microscopy and both scanning and transmission electron microscope. Healing of lesions occurred in two ways, and these were related to lesion size. Small lesions healed by a process of rosette formation, and large lesions were repaired by a process of endothelial dedifferentiation and migration. All damaged areas were re-covered with endothelial cells within 24 hours of exposure, and at this time corneal thickness had returned to control levels. The implications are discussed in relation to the phacoemulsification procedure.

Tannin as an Agent to Eliminate Adhesiveness of Walleye Eggs during Artificial Propagation

Abstract Tannin has been used to decrease adhesiveness of walleye (Stizostedion vitreum) eggs for the purpose of shortening the water-hardening phase of walleye propagation. In this study, adhesiveness of fertilized walleye eggs decreased after exposure to tannin concentrations between 200 and 1,000 mg/liter. Reduction in adhesiveness was generally proportional to tannin concentration and exposure time. Adhesiveness was further reduced and eliminated in higher tannin concentrations by stirring the eggs during a 2-minute exposure. Hatching success of nontreated (control) eggs averaged 37 and 47 percent whereas hatching success of tannin-treated eggs averaged 38 and 50 percent for 1974 and 1975, respectively. A 2-minute exposure at tannin concentrations ranging from 400 to 1,000 mg/liter would expedite artificial propagation and could enhance egg survival.

Behavior of Thoracic Spiracles of Aedes Mosquitoes1 in Controlled Relative Humidities

Observations were made on the behavior of the thoracic spiracles of A. triseriatus (Say) and A. aegypti (L.) in high (90±5%) and low (<5%) relative humidities. Following a 5-minute exposure to low relative humidity, spiracular responses to 0.5% carbon dioxide were reduced in both species while only A. triseriatus showed attenuated spiracular behavior after a 2-minute exposure. Conservative spiracular opening was observed in both unfed and fed mosquitoes. It is postulated that the spiracular response to low relative humidity is a sensory one.

Electrostatic sensitivity of the photo-receptive mechanism in germinating ?Grand Rapids? lettuce seed

Germination of "Grand Rapids" lettuce seed can be influenced by a 2-minute exposure to artificial electrostatic fields of 75 V cm(-I). To a limited extent, electrostatic treatment can substitute for red light by raising the dark germination level. Significant increases in germination, averaging up to 10%, were also observed following electrostatic treatment during, or after, short periods of red irradiation. In contrast, pre-irradiation treatment repressed germination slightly but significantly. An interaction with the phytochrome system is implied by the lack of any significant electrostatic influence after longer periods of red irradiation.

Radioxenon Brain Scanning with the Gamma-Ray Scintillation Camera

Cerebral blood flow has been studied with Xe133 (2, 4) and Kr85 (3) by externally monitoring the rate of disappearance of the radionuclide from the brain after inhalation of the gas or after a carotid artery injection of the gas dissolved in saline. The desaturation curves obtained with Xe133 consist of two (4) or three (2) exponential components; a fast component of T½ one and a half minutes and a slow component of T½ ten minutes (4). These purportedly reflect the cortical and white matter blood flow, respectively. The relatively quick disappearance of the radionuclide precludes scanning by conventional rectilinear apparatus, but the gamma-ray scintillation camera (Pho/Gamma, Nuclear-Chicago) is capable of imaging the brain in as short a time as thirty seconds for the dose of Xe133 used. This feature permitted an investigation of Xe133 as a test agent for scanning. It was administered via the carotid artery and/or inhalation, and a comparison was made, when possible, with the brain scan obtained with macroaggregates of radioiodinated albumin (MARIA) (5, 6). Fifteen patients received the intracarotid injection of Xe133. Their lesions consisted of primary and secondary tumor, cerebral hematoma, and transient vascular ischemia. Method and Material The Xe133 gas was administered through a closed-system device improvised from a discarded McKesson anesthetic gas apparatus. About 15 mCi Xe133 were used, and the expired carbon dioxide was absorbed from the gaseous mixture. A face mask was applied to semicomatose patients; otherwise a mouthpiece was preferred. The patient was instructed to breathe normally. Imaging with the gamma camera commenced when a steady state was reached. Following this, the gas mixture was shunted to a collecting bag, and room air was admitted for inhalation. Two or three 2-minute exposure scintiphotos were obtained during this desaturation phase. Approximately 10 mCi Xe133 dissolved in 10–20 ml of saline was injected into the carotid artery over a thirty-second interval. The gamma camera was set to image the brain during this injection period, and serial half- to one-minute exposure scintiphotos were obtained during the washout. The MARIA was injected into the carotid artery following the xenon-solution study when the two procedures were combined. Approximately 150 μC I131, containing about 1 mg of albumin, was the usual dose. The particle size ranged from 5 to 30 microns in diameter. Results An example of a normal occipital and left lateral Xe133 ventilation scan obtained during the steady state is shown in Figure 1. The results of scans of 6 patients are shown in Figures 2–7. It will be seen that a recurring theme in the case histories is that in spite of the tumor being relatively avascular and cystic, the amount of Xe133 diffusing into the area did not differ greatly from that in the adjacent tissue. Discussion With MARIA injections, the macroaggregates are trapped in the capillaries or distal arterioles.