Sec Off Research Articles

IN VIVO DIAPHRAGMATIC LENGTHENING CONTRACTIONS AND THE RELATIONSHIP TO FORCE PRODUCTION IN THE RABBIT 1639

Lengthening contractions (CL) are known to cause injury in limb skeletal muscle. It is unknown whether the diaphragm (DPM), the primary muscle of inspiration, could be induced to undergo CL in vivo and whether DPM injury occurs as a result. We hypothesized that the DPM could be stimulated to undergo lengthening contractions at physiologic frequencies in vivo and that DPM muscle would decrease following CL, indicating injury. We studied 4 anesthetized (Ketamine/Xylazine), supine, intubated, and mechanically ventilated female New Zealand White rabbits (3.15 ± 0.99 kg). Pressure of the airway opening (Pao) was measured as an indicator of force generating capacity of the DPM. Changes in midcostal diaphragm fiber length were measured via surgical implantation of sonomicrometer crystals (1mm diam). CL were induced by superimposing bilateral transvenous phrenic stimulations of the DPM at 20 Hz (duty cycle: 30 sec on/30 sec off) on mechanical ventilation(tidal volume = 20 ml, frequency = 25/min) for ten minutes. Changes in force production were evaluated by measuring frequency-pressure curves prior to, 5 minutes post CL, and 30 minutes post CL. Mean airway opening pressures were 100.12 ± 3.26% and 116 ± 4.68% of control values(N.S.) at 5 and 30 minutes post CL respectively. Under these experimental conditions, there is no CL induced force decrement indicative of damage to the intact rabbit diaphragm.

Comparative investigation of retinal responses to brief light stimuli: 2-amino-4 -phosphonobutyrate studies-II. Turtle retina ( Emys orbicularis)

1. Electroretinogram (ERG) and responses of single ganglion cells to 75 μsec light flashes, presented on two different backgrounds, were studied. Additionally, stimulation with long lasting stimuli (ordinarily 5 sec ON-, 15 sec OFF-) was used. 2. 2-amino- 4-phosphonobutyrate (APB) at a concentration of 450 μM on average was used to separate OFF- from ON- channels. It is known, that in other species APB selectively blocks the activity of ON-channel only. 3. The existence of APB- sensitive membrane receptors was demonstrated in the turtle retina. As in other species, APB abolished the ERG b-wave and enhanced the d-wave, when long lasting stimulation was used. 4. By means of APB, two components were shown to exist in the ERG positive wave in response to a flash. APB abolished the first component and did not influence or enhanced the second one. 5. By means of APB, one or two components in the impulse activity in response to flash were demonstrated, depending on the type of ganglion cell (ON-, OFF- or ON-OFF). The latency of the first component was 70 msec and the latency of the second one 210 msec on average. APB abolished the first component, and enhanced the second one. 6. The data obtained show that both ON- and OFF- channels take part in the generation of the turtle retinal responses to brief stimuli. 7. Based on the results obtained, some peculiarities of the network organization of the ganglion cells' receptive fields are discussed.

Comparative investigation of retinal responses to brief light stimuli: 2-amino-4-phosphonobutyrate studies—I. Frog retina, Rana ridibunda

1. Electroretinogram (ERG) and responses of single ganglion cells to 75 μsec light flashes, applied at two different backgrounds, were studied. Additionally, a stimulation with long-lasting stimuli (ordinarily 5 sec ON-, 5 sec OFF-) was used. Both white and coloured light stimuli were presented. 2. 150 μM 2-amino- 4-phosphonobutyrate (APB) was used to separate OFF- from ON- channels. 3. Before APB application, one or two components in the impulse activity in response to a flash were observed, depending on the type of ganglion cell (ON-, OFF- or ON-OFF). the latency of the first component was 60 msec and the latency of the second one was from 160 to 430 msec on average, at different background conditions. APB abolished the first component and enhanced the second one. 4. By means of APB, two components were shown to exist in the main positive wave of the flash ERG. APB abolished the first component and did not influence or enhance the second one. 5. The data obtained show that both ON- and OFF- channels take part in the generation of the frog retinal responses to brief stimuli.

Effects of 45-Hz Magnetic Fields on Cortical Eeg Spectrum in Rats

The effects of intermittent (1 sec on/1 sec off) 45-Hz magnetic fields on quantitative electroencephalogram (EEG) were studied using 12 female rats. The animals were exposed for 24 hr to three different conditions: 1000 A/m (1.26 mT), 100 A/m (126 μT), and sham exposure. The cortical EEG was recorded before and after each exposure, and the power spectrum of the EEG was calculated. Exposure at 100 A/m produced statistically significant decreases in the delta (1-4 Hz) and theta (4-8 Hz) bands and increased activities in the beta (12-20 Hz) and 30-60 Hz bands. Smaller changes were seen at 1000 A/m than at 100 A/m. The changes seen were more pronounced 15 min after the end of exposure than immediately after it. At 30 min after exposure most differences from the pre-exposure values had disappeared.

Expression of c-fos protein in rat brain elicited by electrical stimulation of the pontine parabrachial nucleus

The expression of Fos, the protein product of the primary response gene c-fos, was used metabolically to map the short-term (1 hr) effects of urethane and sodium pentobarbital anesthesia in rat. Subsequently, urethane-anesthetized rats were used to study the integrated response to electrical stimulation (1-1.5 hr) of the pontine parabrachial nucleus (PBN), an important center for relay of autonomic information in the brain. Immunohistochemistry was used to localize Fos-like immunoreactivity (FLI) in the brain. To approximate amounts of FLI in the conscious animal, rats were killed immediately after attaining surgical anesthesia with sodium pentobarbital (50 mg/kg) or urethane (1.2-1.7 gm/kg). No FLI was found in the brains of these rats. In rats killed 1 hr after anesthesia with sodium pentobarbital, FLI was found only in the habenulae. After 1 h of urethane anesthesia, low levels of FLI were found in the following areas: nucleus of the tractus solitarius (NTS); caudal and rostral ventrolateral medulla (VLM); lateral PBN; ventromedial, paraventricular, and supraoptic nuclei (SON) of the hypothalamus; medial preoptic area; central nucleus of the amygdala (ACE); endopiriform cortex; insular cortex; piriform cortex; and islands of Calleja. Electrical stimulation of the PBN (10 sec on, 10 sec off; 15-50 microA at 20 Hz for 60-90 min) in rats anesthetized with urethane led to increases in mean arterial pressure (10-30 mm Hg) and to ipsilateral increases of FLI in the lateral PBN, dorsal division of SON, ACE, endopiriform nucleus, insular cortex, piriform cortex, and islands of Calleja. In two animals, ipsilateral increases were found in the ventromedial hypothalamus and medial amygdaloid nucleus.(ABSTRACT TRUNCATED AT 250 WORDS)

対麻痺者のFES立位における筋疲労の影響と原因

Muscle fatigue is one of the serious problems of functional electrical stimulation (FES), because possible standing time is limited by the fatigue. In this study, the three factors of muscle fatigue on FES standing in paraplegia is discussed. First, standing postures with a long leg brace (LLB) and two FES channels were analyzed. The subject was a male, 18-year-old, paraplegic patient with a T8 spinal cord injury. The knee joint flexion moment was calculated from the relationship between the zero moment point of the ground reaction force and the knee joint position. The estimated knee joint flexion moments were 16 Nm (FES) and 28 Nm (LLB). The average moment of three normal subjects was 14 Nm in the extending direction. It was found that the knee joint moment of a paraplegic is significantly greater than that of a normal subject. Knee flexion moment requires a large contraction force of quadriceps. This is one of the reasons for quadriceps fatigue. Second, the properties of muscle fatigue against electrical stimulation in paraplegia and normal subjects were measured. The contractile force decrease by 30 seconds' maximal intensity continuous stimulation varied from 44 to 10 percent in paraplegia. The contractile force decrease in normal subjects was 17 percent on average. The obvious difference between paraplegiacs and normal subjects was not found in the fatigue property. The high-intensity continuous stimulation is a serious problem, because it brings considerable muscle fatigue in both paraplegic and normal subjects. Finally, the fatigue rates caused by the 30 seconds' continuous stimulation and the 60 seconds' alternative stimulation, 3 sec on and 3 sec off, were compared. The alternative stimulation showed a lower fatigue rate. This result shows that stimulation stop or decrease can decrease muscle fatigue. According to this result, an FES standing device was developed. The device was used in the artificial reflex method, one of the stimulation sequences driven by knee joint flexion. In conclusion, three factors were pointed out. 1) Two-channel FES standing requires large quadriceps contractile force. 2) High-intensity continuous stimulation brings serious muscle fatigue. 3) Alternative stimulation decreases the muscle fatigue.

Mural repair following obliteration of aneurysms. Part III: Pathomorphological effects of Nd: YAG laser on aneurysm obliteration

Twenty-four experimental aneurysms were created in rat carotid arteries using the venous pouch technique. Four to twelve weeks later, these aneurysms were totally obliterated by the external application of Nd:YAG laser. The aneurysmal dome and neck were both exposed to the laser using low amplitude (1-2 W) at continuous or repeat intervals (0.3 sec on/0.1 sec off). Small aneurysms were easily obliterated without external signs of necrosis, whereas aneurysms larger than 2 mm required complete coagulation resulting in a charcoal-like appearance. At varying intervals (30 min, 7 days, 3 weeks, 6 weeks), the obliterated aneurysms were harvested and evaluated using the scanning electron microscope and standard histological techniques. The results indicate that the effects of the laser on the aneurysm and parent vessel are similar to those encountered following the application of bipolar coagulation with massive coagulation necrosis of the aneurysmal neck and dome. Notably, however, the extension of this process onto the parent vessel involving especially the endothelium surrounding the aneurysm orifice (commonly seen with bipolar coagulation) is minimal following laser coagulation. There appears to be a protective effect on the parent vessel endothelium by blood flow through the vessel. On this basis, it appears that the laser may be an alternative method of aneurysmal coagulation; the use of laser entails less manipulation of the aneurysm. The Nd:YAG laser may be a useful adjunct in the surgical obliteration of clinical cerebral artery aneurysms, especially small ones.

Motion sickness in guinea pigs (Cavia porcellus) indexed by body rotation-induced conditioned taste aversions

The presence of motion sickness in albino guinea pigs (Cavia porcellus) was examined by using a conditioned taste aversion (CTA) as an index. Eighteen animals were divided into three groups. One group received four pairings of a novel 0.15% saccharin solution followed by 20 min of body rotation at 70 rpm (on a schedule of 15 sec on and 5 sec off). Another group received four pairings of the saccharin solution followed by exposure to sham rotation. The third group experienced the rotation procedure following access to water. The group receiving the rotation procedure contingent on presentation of the novel saccharin taste exhibited a conditioned aversion to this fluid (relative to the control groups) over days of acquisition ( p<0.01), which subsequently dissipated when rotation was no longer contingent on the presentation of the saccharin solution (extinction). These data thus demonstrate the presence of motion sickness in guinea pigs when CTA is used as an index.

The effects of naloxone on body rotation-induced analgesia and anorexia in male mice

The effects of body rotation in a horizontal plane and the opiate antagonist, naloxone, on the nociceptive responses and the feeding behavior of male mice were examined. In the first experiment the mice were rotated (70 rpm, schedule of 15 sec on; 5 sec off) for 60 minutes or exposed to sham rotation for the same duration. Midway through the rotation or sham procedure the mice were either injected with naloxone (1 mg/kg) or isotonic saline. At the end of the 60-minute treatment period the animals were placed on a warm surface (47.5°C) and their latency to show a foot-licking response was measured. The rotation procedure produced a significant ( p<0.01) increase in response latency in the saline-injected mice and the naloxone injections blocked this analgesic effect. This finding provides evidence for opioid involvement in the rotation-induced analgesia. In experiment 2 mice on a food restriction schedule were rotated (70 rpm, 15 sec on; 5 sec off) or sham exposed for 60 minutes. Midway through this treatment period the mice were either injected with naloxone (1 mg/kg) or isotonic saline. Following the treatment period the mice were given access to food for 2 hours. The rotation procedure produced a significant ( p<0.01) reduction in feeding (anorexia) in the first 30 minutes of food access for the saline-injected mice. Injections of naloxone significantly ( p<0.05) enhanced the rotation-induced anorexia. These experiments demonstrate that rotation-induced analgesia in mice is blocked by the opiate antagonist, naloxone, whereas rotation-induced anorexia is not. Further, naloxone was found to enhance rotation-induced anorexia, possibly by intensifying rotation induced motion sickness in the mice.

Differential inhibitory effects of MIF-1, Tyr-MIF-1, naloxone and β-funaltrexamine on body rotation-induced analgesia in the meadow vole, Microtus pennsylvanicus

The effects of body rotation in a horizontal plane and various opiate antagonists on the nociceptive responses of a day-active microtine rodent, the meadow vole, Microtus pennsylvanicus, were examined. Intermittent rotation (70 rpm, schedule of 30 sec on, 30 sec off) for 30 min induced significant analgesic responses in the voles for 15 min after rotation. These increases in thermal response latency were blocked by intraperitoneal pretreatment with either naloxone or the irreversible mu opiate receptor antagonist beta-funaltrexamine (beta-FNA; 10 mg/kg; 24 hr pretreatment). This antagonistic effect of beta-FNA indicates mu opioid involvement in the mediation of rotation-induced analgesia. The antiopiate peptides MIF-1 (Pro-Leu-Gly-NH2) and Tyr-MIF-1 also significantly reduced, though did not completely block, body rotation-induced opiate analgesia. This suggests that Tyr-MIF-1 and MIF-1 have significant antagonistic effects on mu opioid systems that are involved in the mediation of stress (rotation)-induced analgesia.

Transcutaneous muscle stimulation promotes muscle growth in immobilized patients.

Muscular activity is a fundamental determinant of muscle mass. Transcutaneous muscle stimulation (TMS) may reverse muscle atrophy and lean mass loss in immobile patients by "artificial exercise." Four paraplegic patients with upper motor neuron lesions entered The Ohio State University Clinical Research Center for a 21-day metabolic balance study. After 6 days of baseline monitoring, each underwent isometric tetanic contractions (15 sec on; 45 sec off) of all major lower extremity muscle groups with TMS for 10 hr daily. Cross-sectional areas of muscle plus bone were calculated with CAT scan planimetry at 7 levels in both lower extremities before and after the TMS period. Three patients completed the metabolic balance study. TMS produced significant growth of innervated thigh and calf muscles in all paraplegic patients. Little growth occurred where bone and tendon predominate. No significant changes in nitrogen balance (urine and stool excretion), potassium balance (urine excretion only), or phosphate balance (urine excretion only) could be demonstrated. Two possible explanations are (1) that the patients may have been underfed and (2) that perhaps due to an increase in metabolic rate owing to the stimulation, lean tissue in other locations may have been mobilized to meet leg muscle demands. Future studies will incorporate metabolic monitoring of oxygen consumption and CO2 production during the experiment.

Are polyphosphoinositides involved in platelet activation?

In human platelets, the amounts of triphosphoinositides (TPI) and diphosphoinositides (DPI) increase after 30 sec and level off after 120 sec of thrombin stimulation. After 180 sec of thrombin challenge, TPI and DPI increase accounts for 66 and 80%, respectively. Polyphosphoinositide changes roughly parallel the release of N-acetyl-β-D-glucosaminidase and appear as a later event compared to aggregation and serotonin secretion. It is concluded that an increased phosphorylation of polyphosphoinositides might participate in platelets to the process of stimulus-activation coupling and might be linked to thrombin receptor occupancy. A role of DPI in platelet activation is suggested by the observation that DPI promote platelet aggregation, the mechanism of which is discussed.

A 14C-2-Deoxyglucose analysis of the neural pathways of the limbic forebrain in the rat: II. The hypothalamus

An attempt was made to characterize the nature of the functional organization of the hypothalamus by observing the patterns of uptake of 14C-2-deoxyglucose (2DG) following electrical stimulation of different regions within the preoptico-hypothalamus in the rat. The experimental paradigm consisted of electrical brain stimulation delivered continuously for periods of 30 sec on and 30 sec off for 45 minutes following injection of 2DG. Brains were removed and processed for autoradiography. Activation of the medial forebrain bundle was noted following stimulation of the nucleus accumbens and lateral preoptico-hypothalamus. Activated fibers could be followed only in a caudal direction through the medial forebrain bundle and into the ventral tegmental area as a result of nucleus accumbens stimulation. Stimulation of the lateral preoptic region or of the anterior half of lateral hypothalamus produced activation of the lateral septal nucleus, lateral habenular nucleus, perifornical region, midline thalamus and ventral tegmental area. Since stimulation of the perifornical hypothalamus significantly activated the rostro-caudal extent of the midbrain central gray, it is suggested that impulses from the lateral hypothalamus reach the lower brainstem via its connections with the perifornical hypothalamus. Ventromedial hypothalamic stimulation activated only the lateral septal nucleus, cortico-medial amygdala and medial preoptico-hypothalamus, while medial preoptico-hypothalamic stimulation resulted in increased 2DG uptake in the midbrain central gray, thus suggesting that medial hypothalamic impulses reach the brainstem by first ascending to the level of the preoptico-hypothalamus. Mammillary body stimulation orthodromically activated fibers in the mammillothalamic and mammillotegmental tracts and antidromically fibers in the fornix for a short distance.

Ultrasonic treatment of tumors-III high intensity, low frequency exposures

Hamster fibrosarcomas were exposed to 1.06 MHz ultrasound at intensities of 90 W/cm 2 in a pulse mode (0.1 sec on, 0.9 sec off) to avoid excessive heating. Tumor temperatures ranged from 19 to 30°C during these exposures. The treatment had no apparent effect on the rate of growth of the primary tumor or on the rate of metastasis.

Neural lobe of pituitary modulates corticotropin release in the rat.

The hypothesis was tested that the neural lobe of the pituitary may modulate the release of anterior pituitary hormones. The neural lobe of anesthetized lactating rats was electrically stimulated at 30 Hz (5 sec on and 5 sec off) for 3 min while taking blood samples for RIA of ACTH. Plasma ACTH increased within 3 min by 22 +/- 9% (average +/- SEM; P less than 0.025) in intact rats and by 38 +/- 17% (P less than 0.025) in rats where the nerve supply to the median eminence and neural lobe was interrupted. Electrical stimulation of the anterior pituitary was ineffective. No significant changes in plasma ACTH were observed in rats with coagulated hypophysial portal vessels or in Brattleboro rats with congenital diabetes insipidus. Apparently, neither peripheral plasma vasopressin (estimated at 150 microU/ml maximum) nor intermediate lobe ACTH could account for the observed rise in ACTH. Results suggest a vasopressin dependent modulation of ACTH release by the neural lobe, mediated either by axon collaterals to the median eminence or by a vascular interconnection between posterior and anterior pituitaries.

Effect of electrical stimulation of mammary nerve upon pituitary and plasma prolactin concentrations in anesthetized lactating rats.

A 50-70% depletion in the anterior pituitary concentration of PRL occurred within 5 min of electrical stimulation of a single abdominal mammary nerve of urethane-anesthetized lactating rats previously nonsuckled for 6-8 h. The stimulus parameters were: 1-msec pulses, 10-20/sec at 5-30 V applied 5 sec on and 10 sec off. The anterior pituitary concentration of PRL remained low for another 15-30 min after depletion, then repleted to prestimulus levels by the 90th min. The same pattern of depletion-repletion occurred when mammary nerve stimulation was applied for 5 min as when it was applied for 180 min. In other experiments, plasma PRL concentration rose swiftly and attained a maximal level, 4- to 5-fold in Wistar rats and 8- to 10-fold in Holtzman rats, above basal concentrations within 10-15 min of mammary nerve stimulation. The maximal level was sustained throughout the time the nerve was stimulated and for 45 min after the stimulation was stopped, i.e. the sustained secretion of PRL into the plasma occurred at the same time that depleted PRL was repleting. Ligation of both adrenals or iv injection of the beta-adrenergic blocker, propranolol, before stimulation of the nerve had no effect upon the plasma PRL profile in response to mammary nerve stimulation. These data indicate that mammary nerve stimulation mimics that of suckling upon depletion, repletion, and the release of PRL into the circulation and add further support to the hypothesis that these phases are independent processes.

Response of stress-susceptible and stress-resistant Hampshire pigs to electrical stress. I. Physiological and biochemical effects.

Stress susceptible (SS) and stress resistant (SR) purebred Hampshire swine, weighing approximately 100 kg, were utilized to study the effects of electrical stress on plasma creatine phosphokinase (CPK), blood pH, plasma lactic dehydrogenase (LDH), plasma glucocorticoids, rectal temperature, heart rate and respiration rate. Blood samples were obtained from jugular cannulas 15 min and 5 min pre-stress, and subsequently at 0, 5, 10, 15, 30, 60 and 120 min post-stress. The electrical stress (.05 amperes and 30 volts) was administered intermittantly (2 sec on and 1 sec off) directly on the skin at the point of the poll between the ears and on the medial side of the fore leg above the point of the elbow for a total stress time of 4 min over a 6-min period. Each pig was stressed three times with 3 days rest between stimulations. Post-stress responses (P<.01) were obtained over time for all the variables measured except respiration rate. Plasma CPK levels were greater (P<.01) for SS pigs at all the pre-stress and post-stress bleeding times. Thus, CPK may have value in differentiating between SS and SR pigs under standardized environmental (stress) conditions. The SS pigs had marked post-stress decrease (P<.01) in blood pH compared to SR pigs, although pre-stress blood pH was similar for both groups of pigs. Pre-stress plasma LDH levels were similar for the SS and SR pigs while several post-stress levels were greater for the SS pigs. Plasma glucocorticoid levels were similar for the SS and SR pigs at all the pre-and post-stress bleeding times. The SS pigs had a higher (P<.05) overall mean rectal temperature compared to the SR pigs. Both the SS and the SR pigs had elevated post-stress rectal temperatures. The heart rate of the SS pigs was higher at 0 min post-stress compared to the SR pigs while both groups were similar at the other times. Respiration rates were similar for both groups.

Effects of post-trial reinforcing vs. subreinforcing stimulation of the substantia nigra on passive avoidance learning

STAUBLI, U. AND J. P. HUSTON. Effects of post-trial reinforcing vs. subreinforcing stimulation of the substantia nigra on passive avoidance learning. BRAIN RES. BULL. 3(5) 519–524, 1978.—Experiments were designed to investigate the role of post-trial reinforcing and subreinforcing stimulation of the substantia nigra on memory processing. Thirty sec post-trial reinforcing stimulation (0.2 sec on/1.8 sec off) impaired learning of response suppression in a step-down task compared to control animals as well as to animals stimulated at subthreshold current level (i.e., at 25% of the current level shown to maintain optimal self-stimulation in previously performed self-stimulation sessions). In a second small-box passive avoidance experiment, i.e., the alcove-avoidance task, opposite results were attained: Subreinforcing stimulation attenuated learning whereas neither suprathreshold stimulated animals nor control animals showed impairment of learning. The conclusions drawn from these results are as follows: Post-trial stimulation of the substantia nigra interferes with memory processing. This attenuation of learning is obviously task-dependent and can additionally be influenced by the quality of the stimulation, i.e., whether it is reinforcing or not. Possible explanations to account for these task-dependent and quality of stimulation-dependent effects of post-trial substantia nigra stimulation are discussed.

Enhanced passive avoidance learning and appetitive T-maze learning with post-trial rewarding hypothalamic stimulation

Experiments were carried out to investigate the effects of post-trial reinforcing stimulation of the lateral hypothalamus on learning in rats. The reinforcing stimulation was always presented for a duration of 20–30 sec (0.2 sec on/0.8 sec off), and was administered either immediately, 30 sec delayed or 300 sec delayed after exposure to the learning situation. In Experiment 1 post-trial stimulation led to improved passive avoidance learning of an alcove-avoidance task when presented 30 sec compared to immediately after the footshock. In Experiment 2 reversal learning of a one-way shuttle-box avoidance task was facilitated by 30 sec delayed, but not 300 sec delayed post-trial reinforcing stimulation. In Experiment 3 appetitive left-right discrimination was investigated using a T-maze task. Thirty sec delayed post-trial reinforcing stimulation presented contingent on errors facilitated learning of this task. Together, the 3 studies provide further support for the hypothesis that reinforcers directly influence labile memory processes (such as short-term memory) and thereby improve learning.

Small monopropellant thruster contamination measurement in a high-vacuum low-temperature facility

The contamination that results from the exhaust plume of small thrusters used for attitude control maneuvers can pose severe problems for long-life satellite systems. In order to assess this type of contamination problem, analytical and experimental techniques must be developed. Mass deposition rate measurements of a representative 0.44-N thrust hydrazine thruster were made in a space simulation chamber using five appropriately placed variable-temperature quartz crystal microbalances. The mass deposition rates within the thruster plume were measured while operating the thruster over a wide range of operating parameters, including duty cycles, catalyst bed start temperatures, propellant water variation, as well as thruster aging effects. The contamination measurements were made over a temperature range of 144 to 256 K for all duty cycles. In addition, the nominal duty cycle of 100 msec on and 10 sec off was run at a temperature of 106 K. These data will make possible better prediction of deposition rates of contaminants from thrusters used in satellite systems.