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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1996

Calcium kinetics with microgram stable isotope doses and saliva sampling

Studies of calcium kinetics require administration of tracer doses of calcium and subsequent repeated sampling of biological fluids. This study was designed to develop techniques that would allow estimation of calcium kinetics by using small (micrograms) doses of isotopes instead of the more common large (mg) doses to minimize tracer perturbation of the system and reduce cost, and to explore the use of saliva sampling as an alternative to blood sampling. Subjects received an oral dose (133 micrograms) of 43Ca and an i.v. dose (7.7 micrograms) of 46Ca. Isotopic enrichment in blood, urine, saliva and feces was well above thermal ionization mass spectrometry measurement precision up to 170 h after dosing. Fractional calcium absorptions determined from isotopic ratios in blood, urine and saliva were similar. Compartmental modeling revealed that kinetic parameters determined from serum or saliva data were similar, decreasing the necessity for blood samples. It is concluded from these results that calcium kinetics can be assessed with micrograms doses of stable isotopes, thereby reducing tracer costs and with saliva samples, thereby reducing the amount of blood needed.

Clinical Trial↗
NASA NTRS1977

Electrolytes and thermoregulation

The influence of ions on temperature is studied for cases where the changes in ionic concentrations are induced by direct infusion or injection of electrolyte solutions into the cerebral ventricles or into specific areas of brain tissue; intravenous infusion or injection; eating food or drinking solutions of different ionic composition; and heat or exercise dehydration. It is shown that introduction of Na(+) and Ca(++) into the cerebral ventricles or into the venous system affects temperature regulation. It appears that the specific action of these ions is different from their osmotic effects. It is unlikely that their action is localized to the thermoregulatory centers in the brain. The infusion experiments demonstrate that the changes in sodium balance occurring during exercise and heat stress are large enough to affect sweat gland function and vasomotor activity.

Nielsen, B.↗
NASA NTRS1996

Patent Foramen Ovale: Association between the Degree of Shunt by Contrast Transesophageal Echocardiography and the Risk of Future Ischemic Neurologic Events

This study investigated whether there is an association between the degree of interatrial shunting across a patent foramen ovale, as determined by saline contrast transesophageal echocardiography, and the risk of subsequent systemic embolic events, including stroke. Thirty-four patients found to have patent foramen ovale during transesophageal echocardiography were divided into two groups on the basis of the maximum number of microbubbles in the left heart in any single frame after intravenous saline contrast injection: group 1 (n = 16) with a "large" degree of shunt (220 microbubbles) and group 2 (n = 18) with a "small" degree of shunt (23 but <20 microbubbles). Patients were followed up over a mean period of 21 months for subsequent systemic embolic events, including transient ischemic attack and stroke. Five (31%) of the patients with large shunts had subsequent ischemic neurologic events, whereas none of the patients with small shunts had embolic events (p= 0.03). These events occurred in spite of antiplatelet or anticoagulant therapy. We conclude that patients with a large degree of shunt across a patent foramen ovale, as determined by contrast transesophageal echocardiography, are at a significantly higher risk for subsequent adverse neurologic events compared with patients with a small degree of shunt.

Stone, David A.↗
NASA NTRS1995

Effects of angiotensin, vasopressin and atrial natriuretic peptide on intraocular pressure in anesthetized rats

The effects of atrial natriuretic peptide (ANP), vasopressin (AVP) and angiotensin (ANG) on blood and intraocular pressures of pentobarbital anesthetized rats were evaluated following intravenous, intracerebroventricular or anterior chamber routes of administration. Central injections did not affect intraocular pressure. Equipressor intravenous infusions of ANG raised, whereas AVP decreased, intraocular pressure. Direct infusions of a balanced salt solution (0.175 microliter/min) raised intraocular pressure between 30 and 60 min. Adding ANG or ANP slightly reduced this solvent effect but AVP was markedly inhibitory. An AVP-V1 receptor antagonist reversed the blunting of the solvent-induced rise by the peptide, indicating receptor specificity. Acetazolamide pretreatment lowered intraocular pressure, but the solvent-induced rise in intraocular pressure and inhibition by AVP still occurred without altering the temporal pattern. Thus, these effects appear unrelated to aqueous humor synthesis rate. The data support the possibility of intraocular pressure regulation by peptides acting from the blood and aqueous humor.

NASA Discipline Number 14-10↗
NASA NTRS1972

Rare-gas effects on metabolism and inert gas narcosis

The detailed examination is reported of the theory that narcosis results from expansion of the cell membrane under high partial pressures. The research is partially based on the hypothesis that, like oxygen toxicity, the mechanism of metabolic effects of rare gases may be similar at both low and high pressures and are simply more observable at high pressures. Using adult female goats, the parameters measured include oxygen consumption, CO2 production, respiration rate, heart rate, rectal and skin temperatures and the analysis of electroencephalograms and evoked response. Additionally, the specific activity is measured of plasma glucose subsequent to injection of glucose-UL-C-14, intravenous infusion, specific activity of expired CO2, unesterified fatty acid levels and whole blood lactate-to-pyruvate ratios. Also studied were the effects of acetylsalicylic acid, vitamin E and cationic detergents (which alleviate narcosis) upon metabolic changes induced by high pressure narcosis.

Source record↗
NASA NTRS2013

Design Constraints Regarding The Use Of Fluids In Emergency Medical Systems For Space Flight

The Exploration Medical Capability Project of the Human Research Program is tasked with identifying, investigating and addressing gaps existing gaps in either knowledge or technology that need to be addressed in order to enable safer exploration missions. There are several gaps that involve treatment for emergency medical situations. Some of these treatments involve the handling of liquids in the spacecraft environment which involve gas-liquid mixtures handling, dissolution chemistry and thermal issues. Some of the recent technology efforts include the Intravenous fluid generation (IVGEN) experiment, the In-Suit Injection System (ISIS) experiment, and medical suction. Constraints include limited volume, shelf life, handling biohazards, availability of power, crew time and medical training.

McQuillen, John↗
NASA NTRS1982

The identification of the variation of atherosclerosis plaques by invasive and non-invasive methods

Computer-enhanced visualization of coronary arteries and lesions within them is discussed, comparing invasive and noninvasive methods. Trial design factors in computer lesions assessment are briefly discussed, and the use of the computer edge-tracking technique in that assessment is described. The results of a small pilot study conducted on serial cineangiograms of men with premature atherosclerosis are presented. A canine study to determine the feasibility of quantifying atherosclerosis from intravenous carotid angiograms is discussed. Comparative error for arterial and venous injection in the canines is determined, and the mode of processing the films to achieve better visualization is described. The application of the computer edge-tracking technique to an ultrasound image of the human carotid artery is also shown and briefly discussed.

Selzer, R. H.↗
NASA NTRS1976

Effect of Propranolol on Thyroxine-Induced Changes in Body Temperature and Metabolism During Exercise in Dogs

Effects of thyroxine on temperature and metabolism during exercise were studied in dogs after beta-adrenergic blockade. Dogs performed 60 min treadmill exercise of moderate intensity 5 and 72 h following thyroxine injected s. c. in a single dose of 0.1 mg/kg b.w. Thyroxine increased significantly the lipolytic response to exercise as well as blood lactate (LA) concentrations and rectal temperature (T(sub re)) during exercise as early as 5 h following the hormone administration. The changes became more pronounced 72 h after the injection. At rest T(sub re), blood FFA (free fatty acid) and LA levels in the thyroxine-treated dogs did not differ from the control values, and blood glucose was slightly, but significantly higher. Propranolol given intravenously in a dose of 0.25 mg/kg at 30 min of the exercise performed 72 h following thyroxine injection abolished the plasma FFA rise, and inhibited to a certain extent increases in T(sub re) and blood LA concentrations during the next 30 min of exercise.

Kaciuba-Uscilko, Hanna↗
NASA NTRS1999

Effects of subfornical organ lesions on acutely induced thirst and salt appetite

We examined the role of the subfornical organ (SFO) in stimulating thirst and salt appetite using two procedures that initiate water and sodium ingestion within 1-2 h of extracellular fluid depletion. The first procedure used injections of a diuretic (furosemide, 10 mg/kg sc) and a vasodilator (minoxidil, 1-3 mg/kg ia) to produce hypotension concurrently with hypovolemia. The resulting water and sodium intakes were inhibited by intravenous administration of ANG II receptor antagonist (sarthran, 8 micrograms . kg(-1). min(-1)) or angiotensin-converting enzyme inhibitor (captopril, 2.5 mg/h). The second procedure used injections of furosemide (10 mg/kg sc) and a low dose of captopril (5 mg/kg sc) to initiate water and sodium ingestion upon formation of ANG II in the brain. Electrolytic lesions of the SFO greatly reduced the water intakes, and nearly abolished the sodium intakes, produced by these relatively acute treatments. These results contrast with earlier findings showing little effect of SFO lesions on sodium ingestion after longer-term extracellular fluid depletion.

NASA Discipline Regulatory Physiology↗
NASA NTRS1982

Computer assessment of atherosclerosis from angiographic images

A computer method for detection and quantification of atherosclerosis from angiograms has been developed and used to measure lesion change in human clinical trials. The technique involves tracking the vessel edges and measuring individual lesions as well as the overall irregularity of the arterial image. Application of the technique to conventional arterial-injection femoral and coronary angiograms is outlined and an experimental study to extend the technique to analysis of intravenous angiograms of the carotid and cornary arteries is described.

Selzer, R. H.↗
NASA NTRS1975

Acute pulmonary pathology and sudden death in rats following the intravenous administration of the plasticizer, DI (2-ethylhexyl) phthalate, solubilized with Tween surfactants

Intravenous administration of 200-300 mg/kg of di(2-ethylhexyl)phthalate (DEHP) solubilized in aqueous solutions of several Tween surfactants caused respiratory distress in rats. There was a dose-dependent lethality with death generally occurring within 90 minutes after injection. The lungs from DEHP:Tween treated animals were enlarged, generally darkened, and in some cases showed hemorrhagic congestion. Neither the overt symptoms nor the morphologic alterations resulting from DEHP:Tween administration could be reproduced by intravenous administration of aqueous Tween solutions alone. The absence of pulmonary abnormalities following the intravenous administration of DEHP as an aqueous emulsion given either alone or even as soon as 2 minutes after pretreatment with Tween 80, suggests that the specific in vivo interaction between DEHP and Tween surfactants depends on the prior formation of water-soluble micelles of DEHP.

Schulz, C. O.↗
NASA NTRS1996

Anteroventral Third Ventricle Lesions Attenuate Pressor Responses to Serotonin in Anesthetized Rats

When administered intravenously, serotonin (5-hydroxytryptamine; 5-HT) evokes a triphasic blood pressure response, consisting of the Bezold-Jarisch-associated depressor response, a pressor action, and long-lasting depressor response. Because the pressor response may, in part, be caused by central nervous system (CNS) activation by 5-HT, we predicted that destruction of the anteroventral third ventricle (AV3V) region, an area rich in 5-HT receptors, would attenuate increases in blood pressure to intravenous 5-HT. In anesthetized sham-lesioned and AV3V-lesioned Sprague-Dawley rats. we measured mean arterial pressure (MAP), heart rate (HR), and lumbar sympathetic nerve activity (SNA) to increasing bolus doses of intravenous 5-HT (1, 2.5, 5, 10, 25 microg/kg), before and after blockade of bradycardia using methylatropine (200 microg/kg). In all rats, bolus injections of 5-HT elicited bradycardia accompanied by a fall in lumbar SNA and an initial hypotension followed by a pressor response and a longer lasting hypotensive response. The bradycardia, reduction in lumbar SNA, and both depressor responses were equivalent in sham-lesioned and AV3V-lesioned groups. Importantly, AV3V lesions attenuated pressor responses to increasing doses of 5-HT (3 +/- 1, 6 +/- 4, 6 +/- 4, 17 +/- 4, 35 +/- 3 mmHg) compared to sham-lesioned controls (6 +/- 3, 16 +/- 7, 33 +/- 5, 54 +/- 4, 51 +/- 6 mmHg; P < 0.0001). This attenuation was conserved following blockade of bradycardia with methylatropine (P < 0.01). In summary, pressor responses to intravenous 5-HT are diminished by AV3V lesions. These data indicate that the pressor component of the blood pressure response to intravenous 5-HT is partly dependent upon interaction with the CNS.

Muntzel, Martin S.↗
NASA NTRS2014

Portable Intravenous Fluid Production Device For Ground Use Project

Several medical conditions require the administration of intravenous (IV) fluids,but limitations of mass, volume, shelf-life, transportation, and local resources can restrict the availability of these important fluids. Such limitations are expected in long-duration space exploration missions and in remote or austere places on Earth. This design uses regular drinking water that is pumped through two filters to produce, in minutes, sterile, ultrapure water that meets the stringent quality standards of the United States Pharmacopeia for Water for Injection (Total Bacteria, Conductivity, Endo - toxins, Total Organic Carbon). The device weighs 2.2 lb (1 kg) and is 10 in. long, 5 in. wide, and 3 in. high (≈25, 13, and 7.5 cm, respectively) in its storage configuration. This handheld device produces one liter of medical-grade water in 21 minutes. Total production capacity for this innovation is expected to be in the hundreds of liters. The device contains one battery powered electric mini-pump. Alternatively, a manually powered pump can be attached and used. Drinking water enters the device from a source water bag, flows through two filters, and final sterile production water exits into a sealed, medical-grade collection bag. The collection bag contains pre-placed crystalline salts to mix with product water to form isotonic intravenous medical solutions. Alternatively, a hypertonic salt solution can be injected into a filled bag. The filled collection bag is detached from the device and is ready for use or storage. This device currently contains one collection bag, but a manifold of several pre-attached bags or replacement of single collection bags under sterile needle technique is possible for the production of multiple liters. The entire system will be flushed, sealed, and radiation-sterilized. Operation of the device is easy and requires minimal training. Drinking water is placed into the collection bag. Inline stopcock flow valves at the source and collection bags are opened, and the mini-pump is turned on by a switch to begin fluid flow. When the collection bag is completely filled with the medical- grade water, the pump can be turned off. The pump is designed so it cannot pump air, and overfilling of the collection bag with fluid is avoided by placing an equal amount of water in the source bag. Backflow is avoided by inline check valves. The filled collection bag is disconnected from its tubing and is ready for use. The source bag can be refilled for production of multiple liters, or the source bag can be replaced with an input tube that can be placed in a larger potable water source if the device is attended. The device functions in all orientations independent of any gravity fields. In addition to creating IV fluids, the device produces medical-grade water, which can be used for mixing with medications for injection, reconstituting freeze-dried blood products for injection, or for wound hydration or irrigation. Potential worldwide use is expected with medical activities in environments that have limited resources, storage, or resupply such as in military field operations, humanitarian relief efforts, submarines, commercial cruise ships, etc.

Technology Portfolio System↗
NASA NTRS1992

Comparisons of three anti-G suit configurations during long duration, low onset, +Gz

Little physiologic data exist on the effects of long duration, low onset, hypergravity (+G). Space shuttle crewmembers are subjected to low +G forces (less than +3G) for upwards of 30 minutes during reentry. A similar reentry profile is predicted for the National Aerospace Plane (NASP). The physiologic effects of this acceleration stress are compounded by the loss of body water experienced during microgravity. Currently, a standard 5 bladder anti-G suit is being used during shuttle reentry. There have been complaints of discomfort using this suit, mainly due to the abdominal bladder. This study compared the effectiveness of three anti-G suit configurations in volume depleted subjects during a simulated space shuttle reentry profile. Methods: Seven male subjects were given intravenous Lasix in a dose from 20-40 mg to induce a total body weight loss of 3 plus or minus 1.5 percent. Approximately six hours after the injection, the subjects donned one of three anti-G suits - a standard 5 bladder anti-G suit, an extended coverage anti-G suit (the advanced technology anti-G suit or ATAGS), or an extended coverage anti-G suit without an abdominal bladder (the reentry anti-G suit or REAGS). All subjects were exposed to a simulated space shuttle reentry profile. Non-invasive eye-level blood pressure (ELBP) was monitored throughout the +G exposure. When systolic ELBP dropped below 70 mmHg, the anti-G suit was inflated in 0.5 psig increments to the pressure required to maintain 70 mmHg ELBP. Each subject rode with all three suits. Comparisons were made between the final pressure required in each suit to maintain ELBP and subjective reports of comfort. Results: The mean final suit pressure required to maintain ELBP was 1.1 psi, in both the ATAGS and REAGS versus 1.8 psi in the standard suit. In addition, the subjects rated the REAGS suit highest on the comfort scale, citing the absence of the abdominal bladder as the main reason. Conclusions: Overall, the REAGS suit was the superior anti-G suit during long duration, low onset +G. This is based on its ability to maintain ELBP and still remain comfortable when inflated for prolonged periods of time.

Stegmann, B. J.↗
NASA NTRS1997

Vagal and sympathetic mechanisms in patients with orthostatic vasovagal syncope

BACKGROUND: Autonomic and particularly sympathetic mechanisms play a central role in the pathophysiology of vasovagal syncope. We report direct measurements of muscle sympathetic nerve activity in patients with orthostatic vasovagal syncope. METHODS AND RESULTS: We studied 53 otherwise healthy patients with orthostatic syncope. We measured RR intervals and finger arterial pressures and in 15 patients, peroneal nerve muscle sympathetic activity before and during passive 60 degree head-up tilt, with low-dose intravenous isoproterenol if presyncope did not develop by 15 minutes. We measured baroreflex gain before tilt with regression of RR intervals or sympathetic bursts on systolic or diastolic pressures after sequential injections of nitroprusside and phenylephrine. Orthostatic vasovagal reactions occurred in 21 patients, including 7 microneurography patients. Presyncopal and nonsyncopal patients had similar baseline RR intervals, arterial pressure, and muscle sympathetic nerve activity. Vagal baroreflex responses were significantly impaired at arterial pressures below (but not above) baseline levels in presyncopal patients. Initial responses to tilt were comparable; however, during the final 200 seconds of tilt, presyncopal patients had lower RR intervals and diastolic pressures than nonsyncopal patients and gradual reduction of arterial pressure and sympathetic activity. Frank presyncope began abruptly with precipitous reduction of arterial pressure, disappearance of muscle sympathetic nerve activity, and RR interval lengthening. CONCLUSIONS: Patients with orthostatic vasovagal reactions have impaired vagal baroreflex responses to arterial pressure changes below resting levels but normal initial responses to upright tilt. Subtle vasovagal physiology begins before overt presyncope. The final trigger of human orthostatic vasovagal reactions appears to be the abrupt disappearance of muscle sympathetic nerve activity.

Non-NASA Center↗
NASA NTRS2007

Bisphosphonate Treatment: Risk Management in Long Duration Spaceflight

Bisphosphonates are a class of pharmaceuticals used to treat diverse bone disorders such as osteoporosis, Paget's disease, and multiple myeloma. They constitute a class of drugs which adhere to bony surfaces and interfere with the resorptive activity of osteoclasts. They also represent a potential countermeasure towards the loss of bone mass experienced by astronauts during spaceflight. Recently, the medical literature has revealed cases of osteonecrosis of the jaw in individuals receiving intravenous bisphosphonate therapy with a smaller number of cases occurring in individuals receiving the oral form of the medication. Risk management for long duration missions requires consideration of mission success and lifetime health care of astronauts. We performed MEDLINE and PubMed searches (1966 December 2006) using the following keywords: osteonecrosis, jaw, bisphosphonates. Additional references were obtained from the citations of the retrieved articles. Injectable bisphosphonates such as pamidronate and zoledronic acid have been highlighted recently in the literature due to a possible link with osteonecrosis of the jaw. The mechanism of action remains unclear but may be linked to physiologic microdamage in the jawbones resulting from suppression of bone metabolism. The most predisposing factors appear to be the type and dose of bisphosphonate used, a history of dental surgery, trauma, and/or dental infection. In addition, patients diagnosed with a malignancy such as breast cancer or multiple myeloma, who have been on intravenous bisphosphonate therapy for several months seem to be at increased risk. The use of oral bisphosphonates appears to place patients more at risk from acute events such as gastrointestinal tract injury or perforation. Although some studies report little to no increase in GI events compared to placebo, we must remember that in microgravity, astronauts may be unable to comply with medication instructions. They may have difficulty remaining upright for the required 30-45 minutes post-ingestion. We are currently unaware if this inability to comply with instructions on the package insert may lead to an increased risk for GI events. There is a potential long-term complication that resides with both forms of bisphosphonate therapy. In order to repair normally occurring physiologic microdamage to bone, both osteoclastic resorption and osteoblastic bone deposition must be functional. Controversy exists in the literature regarding whether prolonged use of bisphosphonates may lead to the suppression of bone turnover and accumulation of microdamage. Bisphosphonates are a powerful class of drugs that suppress bone turnover, but may cause serious adverse clinical events such as gastrointestinal tract injury or osteonecrosis of the jaw. Unfortunately, little to no data exists currently which may help us provide answers regarding the risks of their use in a healthy astronaut cohort. While controversy exists in the literature regarding their mechanism and long-term consequences, the potential mission impact or lifetime health care impact of an adverse clinical event resulting from bisphosphonate therapy must be considered.

Fogarty, Jennifer A.↗
NASA NTRS1993

Physiological water model development

The water of the human body can be categorized as existing in two main compartments: intracellular water and extracellular water. The intracellular water consists of all the water within the cells and constitutes over half of the total body water. Since red blood cells are surrounded by plasma, and all other cells are surrounded by interstitial fluid, the intracellular compartment has been subdivided to represent these two cell types. The extracellular water, which includes all of the fluid outside of the cells, can be further subdivided into compartments which represent the interstitial fluid, circulating blood plasma, lymph, and transcellular water. The interstitial fluid surrounds cells outside of the vascular system whereas plasma is contained within the blood vessels. Avascular tissues such as dense connective tissue and cartilage contain interstitial water which slowly equilibrates with tracers used to determine extracellular fluid volume. For this reason, additional compartments are sometimes used to represent these avascular tissues. The average size of each compartment, in terms of percent body weight, has been determined for adult males and females. These compartments and the forces which cause flow between them are presented. The kidneys, a main compartment, receive about 25 percent of the cardiac output and filters out a fluid similar to plasma. The composition of this filtered fluid changes as it flows through the kidney tubules since compounds are continually being secreted and reabsorbed. Through this mechanism, the kidneys eliminate wastes while conserving body water, electrolytes, and metabolites. Since sodium accounts for over 90 percent of the cations in the extracellular fluid, and the number of cations is balanced by the number of anions, considering the renal handling sodium and water only should sufficiently describe the relationship between the plasma compartment and kidneys. A kidney function model is presented which has been adapted from a previous model of normal renal function in man. To test the validity of the proposed kidney model, results predicted by the model will be compared to actual data involving injected or ingested fluids and subsequent urine flow rates. Comparison of the model simulation to actual data following the ingestion of 1 liter of water is shown. The model simulation is also shown with actual data following the intravenous infusion of hypertonic saline.

Doty, Susan↗
NASA NTRS1978

Influence of central venous pressure upon sinus node responses to arterial baroreflex stimulation in man

Measurements were made of sinus node responses to arterial baroreceptor stimulation with phenylephrine injection or neck suction, before and during changes of central venous pressure provoked by lower body negative pressure or leg and lower truck elevation. Variations of central venous pressure between 1.1 and 9.0 mm Hg did not influence arterial baroreflex mediated bradycardia. Baroreflex sinus node responses were augmented by intravenous propranolol, but the level of responses after propranolol was comparable during the control state, lower body negative pressure, and leg and trunk elevation. Sinus node responses to very brief baroreceptor stimuli applied during the transitions of central venous pressure also were comparable in the three states. The authors conclude that physiological variations of central venous pressure do not influence sinus node responses to arterial baroreceptor stimulation in man.

Mark, A. L.↗