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At least 1,153 records · Page 64Linked to original sources
PubMed1979

Isotopically labelled compounds in the study of extracellular fluid space in dog bone.

The extracellular fluid space in dog bone has been examined using a series of isotopically labelled compounds. Sodium-77 bromide and indium-113m ethylenediaminetetracetic acid were used as extracellular fluid space markers, radioactive water as a total fluid space marker, and potassium-43 chloride to examine the existence of a bone membrane. The clearance of each tracer from bone was monitored for a period of 2h post-injection. Graphical analysis of the clearance curves shows that the number of exponential functions vary depending on the type of tracer used. The fact that a sum of three exponential terms can completely describe each curve indicates that a simple model consisting of three compartments is sufficient to approximate the clearance of these tracers from bone and its associated fluid space. It is concluded that bone consists of an extracellular fluid space, and that this space may well play an important part in the transference of solutes and the mechanisms involved in their localization on the hydroxyapatite crystals of bone.

Animals↗
PubMed1983

Alterations in calcium homeostasis and bone during actual and simulated space flight.

The weightlessness experienced in space produces alterations in calcium homeostasis. Gemini, Apollo, and Skylab astronauts exhibited a negative calcium balance due primarily to hypercalciuria. In addition, the bone mineral density of the calcaneus declined by approximately 4% in Skylab crew members after 84 d of orbital flight. The negative calcium balance and loss of calcaneal bone mineral in normal adults subjected to prolonged bed rest was comparable to that observed in space. The pathogenesis of bone loss during space flight and bed rest is not well understood due to the lack of histomorphometric data. It is also uncertain whether osteoporotic changes in astronauts are corrected postflight. The observed bone loss would be reversible and of no long-term consequence if the only abnormality was an increased remodeling rate. However, altered bone cell activity would probably result in irreversible bone loss with the premature development of senile osteoporosis many years after space flight. The main skeletal defect in growing rats placed in orbit aboard Soviet Cosmos biosatellites appears to be diminished bone formation. Bone resorption was not elevated during weightlessness. Although cortical bone returned to normal postflight, the decline in trabecular bone mass was somewhat persistent. These studies established that the modeling of a growing skeleton was altered in a weightless environment, but do not necessarily imply that a remodeling imbalance occurs in adults during space flight. However, various forms of simulated space flight inhibited bone formation during both skeletal modeling and the remodeling of adult bone.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

The endocrine and metabolic responses to space flight.

The absence of hydrostatic forces, which results in body fluid shifts, and the absence of deformation forces on normally load-bearing tissues, appear to cause the principal disturbances found during and after space flight in the cardiovascular, fluid and electrolyte, erythropoietic, musculoskeletal, and metabolic systems. These alterations produce reduced body fluid volume, reduced musculoskeletal mass, and alterations in basal metabolism, resulting in the following consistent findings of space flight: weight loss, altered body composition, decreased orthostatic tolerance, and a compromised ability to deal with physical activity after returning from a space-flight environment. Specific changes include alterations in hydration status, resulting in a relative dehydration, loss of body calcium stores with a concomitant increase in urinary hydroxyproline, skeletal muscular atrophy, and a negative energy balance after prolonged space flight. Numerous endocrine changes have been determined during space flight, but more sensitive assay developed recently will allow careful determination of other hormone levels, and measurement of some of the primary changes that occur during the first hours of space flight. These results will be integrated into a working systems model of the physiologic response to weightlessness.

Atrophy↗
PubMedDate not supplied

[The comparative characteristics of crystalline lens and limb regeneration in newts operated on before and after the completion of an orbital space flight].

It has been already established that a tendency towards synchronization and acceleration of the forelimb and lens regeneration is observed in Pleurodeles waltlii under the effect of space flight factors. Here we present the results obtained after 16-day space flight of two groups of newts. In animals of group I forelimbs were amputated and lenses were removed 14 and 7 days before the space flight, respectively. Intact animals of group II were operated on the day of the sputnik landing. Regenerates of the flight and corresponding control animals were fixed at the same time after the operation. For evaluation of the regeneration rate morphological criteria were used: morphological stages of regeneration were compared in the experiment and the control. For quantitative assay of the regeneration rate we determined the index of nuclei labelled with 3H-thymidine in the blastema and lens rudiment cells and used morphometry of the lens regenerates. Acceleration of forelimb and lens regeneration was observed in both groups of animals. In group II more than two-fold increase of the index of labelled nuclei was found in the blastema cells at the comparable stages of development. The size of lens regenerates in flight groups I and II exceeded reliably those in the control animals. The results obtained suggest a prolonged effect of the space flight factors on forelimb and lens regeneration. Under the conditions of space flight the lens regenerates reached more advanced stages of regeneration, as compared with the control animals operated after the space flight. These results also suggest acceleration of regeneration in lower vertebrates.

Amputation, Surgical↗
PubMedDate not supplied

A multivariate model to predict the distance from the skin to the epidural space in an obstetric population.

BACKGROUND AND OBJECTIVES: Several attempts to relate epidural space depth to individual patient parameters or details of technique have yielded modest correlations. An attempt has been made to construct a multivariate model to predict the depth from the skin of the epidural space with use of several such factors. METHODS: The depth of the epidural space from the skin was measured in 263 obstetric patients by using calibrated needles. In 53 patients, the angle of insertion of the epidural needle was also measured, with protractors. For each patient, 14 descriptors of patient habitus and anesthetic technique were recorded. Multiple regression analysis was used to construct models incorporating combinations of these variables to predict the epidural space depth; the model balancing the highest correlation coefficient and greatest statistical significance was selected. The validity of the model was tested on the 53 patients in whom the angle of the needle had been measured but whose data have not been used to construct the model. RESULTS: A model containing the seven variables present-weight, height, body mass index, age, parity, interspace, and patient position-yielded r = .689, < .0001. This model predicted the depth of the epidural space to within 8 mm and predicted the depth in the validation group well. Correction for the angle of insertion of the needle did not improve the predictive power of the model. CONCLUSIONS: While this model is the best predictor of epidural space depth yet published, it is probably not sufficiently accurate to be clinically useful in confirming proper epidural catheter placement. Further work in this area is probably not justified.

Anesthesia, Epidural↗
PubMed1997

Pulmonary function in space.

The lung is exquisitely sensitive to gravity, and so it is of interest to know how its function is altered in the weightlessness of space. Studies on National Aeronautics and Space Administration (NASA) Spacelabs during the last 4 years have provided the first comprehensive data on the extensive changes in pulmonary function that occur in sustained microgravity. Measurements of pulmonary function were made on astronauts during space shuttle flights lasting 9 and 14 days and were compared with extensive ground-based measurements before and after the flights. Compared with preflight measurements, cardiac output increased by 18% during space flight, and stroke volume increased by 46%. Paradoxically, the increase in stroke volume occurred in the face of reductions in central venous pressure and circulating blood volume. Diffusing capacity increased by 28%, and the increase in the diffusing capacity of the alveolar membrane was unexpectedly large based on findings in normal gravity. The change in the alveolar membrane may reflect the effects of uniform filling of the pulmonary capillary bed. Distributions of blood flow and ventilation throughout the lung were more uniform in space, but some unevenness remained, indicating the importance of nongravitational factors. A surprising finding was that airway closing volume was approximately the same in microgravity and in normal gravity, emphasizing the importance of mechanical properties of the airways in determining whether they close. Residual volume was unexpectedly reduced by 18% in microgravity, possibly because of uniform alveolar expansion. The findings indicate that pulmonary function is greatly altered in microgravity, but none of the changes observed so far will apparently limit long-term space flight. In addition, the data help to clarify how gravity affects pulmonary function in the normal gravity environment on Earth.

Humans↗
PubMedDate not supplied

[Organ and tissue regeneration in lower vertebrate animals during space flight and after its completion].

The most important data obtained in studies of the influence of space flight factors on the limb and lens regeneration in the newt Pleurodeles waltlii have been summarized. Regeneration of these organs under the conditions of space flight and after its termination proceeded just as on the ground. However after the 7th, 13th and 16th days of space flight, a trend was shown toward acceleration of the limb and lens regenerates development according to the regeneration stages and synchronization of the achieved stages, which was accompanied in some cases by an increased proliferative activity of the regenerate cells. It was shown that in two groups of animals operated before the 16-day space flight (I) and just after its termination (II) accelerated development of the limb and lens regenerates was observed. In group II, at the large bud stage, the index of 3H-thymidine labeled blastema cells was more than twice that in the control. The size of regenerates in groups I and II exceeded reliably those in the control. These results suggest a prolonged effect of space flight factors on the limb and lens regeneration. It was also shown that the capacity of the muscle minced 14 days before the flight for regeneration was not suppressed, although somewhat decreased. An electron microscopic study showed degenerative-atrophic changes in the intact hind limb muscle after the 16-day space flight. We believe that the phenomenon of synchronization and accelerated regeneration of the limb and lens observed in the most experiments are due to the effect of microgravity on the animals.

Animals↗
PubMed2001

Voluntary head stabilisation in space during oscillatory trunk movements in the frontal plane performed before, during and after a prolonged period of weightlessness.

The ability to voluntarily stabilise the head in space exhibited by two subjects during lateral rhythmic oscillations of the trunk has been investigated before, during and after a prolonged period of microgravity (microG) exposure. In flight acquisitions were performed onboard the Core Module of the Russian Space Station MIR as part of the T4 "Human Posture in Microgravity" experiment of the 179-days ESA-RKA mission EUROMIR-95. Data collection and kinematic analysis were performed by means of a space-qualified version of the automatic motion analyser ELITE. Head stabilisation in space strategy was estimated by means of the head anchoring index and cross-correlation analysis. Results show that head orientation may be well stabilised about the roll axis both with and without the presence of visual information. This was true despite the expected reduction in vestibular efficiency and muscular proprioception occurring in-flight. In one subject, however, vision was found to improve head stabilisation in space post-flight, presumably to recover from the postural deficiency induced by the long-term microG exposure. Head stability during trunk movements was achieved with either over-compensatory (out-of-phase), under-compensatory (in-phase) or mixed movement strategies, as was attested by the analysis of cross-correlation functions between head and shoulder movements. In weightlessness, vision occlusion seemed to influence the choice of the strategies to be used as well as the reduction of movement variability. The feedforward nature of compensatory head movements suggests that head stabilisation could be based in weightlessness on the internal postural body scheme, supposed to be adapted to the weightless environment within 5 months of microG exposure.

Adaptation, Biological↗
PubMed1988

Space Station habitability research.

The purpose and scope of the Habitability Research Group within the Space Human Factors Office at the NASA/Ames Research Center is described. Both near-term and long-term research objectives in the space human factors program pertaining to the U.S. manned Space Station are introduced. The concept of habitability and its relevancy to the U.S. space program is defined within a historical context. The relationship of habitability research to the optimization of environmental and operational determinants of productivity is discussed. Ongoing habitability research efforts pertaining to living and working on the Space Station are described.

Environment Design↗
PubMed1995

Extravehicular activity space suit interoperability.

The European Agency (ESA) and the Russian Space Agency (RKA) are jointly developing a new space suit system for improved extravehicular activity (EVA) capabilities in support of the MIR Space Station Programme, the EVA Suit 2000. Recent national policy agreements between the U.S. and Russia on planned cooperations in manned space also include joint extravehicular activity (EVA). With an increased number of space suit systems and a higher operational frequency towards the end of this century an improved interoperability for both routine and emergency operations is of eminent importance. It is thus timely to report the current status of ongoing work on international EVA interoperability being conducted by the Committee on EVA Protocols and Operations of the International Academy of Astronauts initiated in 1991. This paper summarises the current EVA interoperability issues to be harmonised and presents quantified vehicle interface requirements for the current U.S. Shuttle EMU and Russian MIR Orlan DMA and the new European/Russian EVA Suit 2000 extravehicular systems. Major critical/incompatible interfaces for suits/mother-craft of different combinations are discussed, and recommendations for standardisations given.

Equipment Design↗
PubMed1992

Human reproductive issues in space.

Animal studies in space or analogous environments have suggested that there may be problems in the reproductive sphere; such factors might limit mankind's ability to live and work for extended periods of time in microgravity or on non-terrestrial planetary surfaces. A review of reproductive functioning in animal species studied during space flight demonstrated that most species were affected significantly by the absence of gravity and/or the presence of radiation. These two factors induced alterations in normal reproductive functioning independently of, as well as in combination with, each other. Based on animal models, we have identified several potential problem areas regarding human reproductive physiology and functioning in the space environment. While there are no current space flight investigations, the animal studies suggest priorities for future research in human reproduction. Such studies will be critical for the successful colonization of the space frontier.

Animals↗
PubMed1998

Applications of telemedicine in the United States space program.

Since the beginning of human space flight, NASA has been placing humans in extreme and remote environments. There are many challenges in maintaining humans in outer space, including the provision of life-support systems, radiation shielding, and countermeasures for minimizing the effect of microgravity. Because astronauts are selected for their health, among other factors, disease and illness are minimized. However, it is still of great importance to have appropriate medical care systems in place to address illness and injury should they occur. With the exception of the Apollo program, exploration of space has been limited to missions that are within several hundred miles of the surface of the Earth. At the drawn of the 21st century and the new millennium, human exploration will be focused on operation of the International Space Station (ISS) and preparation for human missions to Mars. These missions will present inherent risks to human health, and, therefore, appropriate plans must be established to address these challenges and risks. Crews of long-duration missions must become more independent from ground controllers. New systems, protocols, and procedures are currently being perfected. Application of emerging technologies in information systems and telecommunications will be critical to inflight medical care. Application of these technologies through telemedicine will provide crew members access to information, noninvasive procedures for assessing health status, and guidance through the integration of sensors, holography, decision-support systems, and virtual environments. These technologies will also serve as a basis to enhance training and medical education. The design of medical care for space flight should lead to a redesign of the practice of medicine on Earth.

Computer Communication Networks↗
PubMed2000

Thermal physiological consideration of precooling procedures in manned space craft.

OBJECTIVE: To explore a space craft precooling temperature at which excessive thermal stress on the crew member could be prevented or reduced in an overheated launch or reentry module. METHOD: Five young male volunteers wearing a space suit participated in 25 tests at sea level. The space suit was either ventilated in a volume air flow rate of 100 L/min (STPD) with ambient air at temperatures (Ta) of 15 degrees C, 10 degrees C, and 5 degrees C, respectively, or not ventilated. Rectal (Tr), mean skin (Tsk) and mean body (Tb) temperatures were measured. RESULT: At Ta 15 degrees C, Tr decreased without significance (from 37.0 +/- 0.2C to 36.7 +/- 0.3 degrees C) in 120-min tests, whereas mean Tsk and mean Tb decreased significantly, and subjects had local cold strain whether the space suit was ventilated or not; while at Ta 10 degrees C, Tr decreased from 37.0 +/- 0.3 degrees C to 36.3 +/- 0.3 degrees C (P < 0.05), subjects had a whole body cold strain, and both mean Tsk and Tb dropped continuously and significantly. CONCLUSION: Ambient temperature 15 degrees C, at which the thermal comfort states of crew was not significantly degraded, was acceptable after precooling in a space craft.

Adolescent↗
PubMed2003

The Chameleon Suit--a liberated future for space explorers.

Mankind's spacefaring future demands the ability to work freely and frequently in space. Traditional spacesuit systems burden both the spacefarer and the mission, limiting the extent to which this is possible. The spacefarer is burdened by a pressure suit designed for isolation from the environment and a life support system designed to replace everything our environment normally provides. The space mission is burdened by this equipment and the expendable materials to operate and maintain it. We aren't free to work in space as frequently, as long, or in all of the locations envisioned. The NASA Institute for Advanced Concepts (NIAC) has sponsored research on an alternative concept, the "Chameleon Suit", that seeks to liberate future explorers and missions from these limitations. The Chameleon Suit system works with the environment in an adaptive fashion to minimize hardware and expendable materials. To achieve this, functions of the life support system are integrated with the pressure suit using emerging materials and design technology. Technologies under study include shape change polymers and electroemissive materials to modify heat transfer characteristics of the spacesuit "skin" achieving thermoregulation analogous to that in natural biological systems. This approach was shown to be feasible for many space missions during the Phase 1 study program. The current Phase 2 program is investigating more aggressive concepts aimed at eliminating most of the hardware currently included in the spacesuit's life support backpack. This paper describes the concept, study results to date, and possible impacts on future human space exploration.

Biomimetic Materials↗
PubMed1996

Neurofilament spacing, phosphorylation, and axon diameter in regenerating and uninjured lamprey axons.

It has been postulated that phosphorylation of the carboxy terminus sidearms of neurofilaments (NFs) increases axon diameter through repulsive electrostatic forces that increase sidearm extension and interfilament spacing. To evaluate this hypothesis, the relationships among NF phosphorylation, NF spacing, and axon diameter were examined in uninjured and spinal cord-transected larval sea lampreys (Petromyzon marinus). In untransected animals, axon diameters in the spinal cord varied from 0.5 to 50 microns. Antibodies specific for highly phosphorylated NFs labeled only large axons (> 10 microns), whereas antibodies for lightly phosphorylated NFs labeled medium-sized and small axons more darkly than large axons. For most axons in untransected animals, diameter was inversely related to NF packing density, but the interfilament distances of the largest axons were only 1.5 times those of the smallest axons. In addition, the lightly phosphorylated NFs of the small axons in the dorsal columns were widely spaced, suggesting that phosphorylation of NFs does not rigidly determine their spacing and that NF spacing does not rigidly determine axon diameter. Regenerating neurites of giant reticulospinal axons (GRAs) have diameters only 5-10% of those of their parent axons. If axon caliber is controlled by NF phosphorylation via mutual electrostatic repulsion, then NFs in the slender regenerating neurites should be lightly phosphorylated and densely packed (similar to NFs in uninjured small caliber axons), whereas NFs in the parent GRAs should be highly phosphorylated and loosely packed. However, although linear density of NFs (the number of NFs per micrometer) in these slender regenerating neurites was twice that in their parent axons, they were highly phosphorylated. Following sectioning of these same axons close to the cell body, axon-like neurites regenerated ectopically from dendritic tips. These ectopically regenerating neurites had NF linear densities 2.5 times those of uncut GRAs but were also highly phosphorylated. Thus, in the lamprey, NF phosphorylation may not control axon diameter directly through electrorepulsive charges that increase NF sidearm extension and NF spacing. It is possible that phosphorylation of NFs normally influences axon diameter through indirect mechanisms, such as the slowing of NF transport and the formation of a stationary cytoskeletal lattice, as has been proposed by others. Such a mechanism could be overridden during regeneration, when a more compact, phosphorylated NF backbone might add mechanical stiffness that promotes the advance of the neurite tip within a restricted central nervous system environment.

Animals↗
PubMed1999

Anatomical spaces: a review.

The meaning and usefulness of the phrase "an anatomical space" are questioned. The concept of anatomical space is examined from historical, developmental, and topographical viewpoints. The validity of the idea and usage of the term "potential space" is discussed. The criterion of Haines (1991) is adopted, that only "spaces" or "cavities" that are lined with a "mesothelial" layer and that can repeatedly be opened up without tissue damage should be considered "true potential spaces." A plea is made that all other anatomical "spaces" be designated "compartments."

Anatomy↗
PubMed2000

Complications of nonlinear echo time spacing for measurement of T (2).

Some consequences of using nonlinear echo spacing in multi-echo sequences for measuring T(2) were investigated under the conditions of imperfect RF refocusing or diffusion losses. Although using nonlinear echo spacing has previously been shown to estimate T(2) more accurately, the effect of such spacing is shown to be detrimental when sequences use imperfect RF refocusing pulses. The progressive loss of transverse magnetization that results from imperfect refocusing will alter estimates of T(2) regardless of the echo spacing. However, when the echo spacing is nonlinear, this loss of magnetization also introduces non-mono-exponential T(2) components. Such an effect may distort relative amplitudes of a multi-component T(2) distribution or generate multiple T(2) components where they do not exist. Diffusion through inhomogeneous magnetic fields results in a similar loss of magnetization and T(2) distortion. For these reasons, the use of nonlinearly spaced echoes, while providing in theory a more appropriate sampling of transverse relaxation, is not appropriate for many imaging situations.

Diffusion↗
PubMed1985

The prognostic significance of lymph-vascular space invasion in stage I endometrial cancer.

Surgical specimens from 111 patients with Stage I endometrial cancer were reviewed for the presence of lymph-vascular space invasion by tumor cells. Lymph-vascular space invasion was noted in 16 cases, and occurred most frequently in poorly differentiated tumors with deep myometrial penetration. Tumor recurrence developed in 44% of patients whose tumors demonstrated lymph-vascular space invasion as opposed to only 2% of patients without this finding (p less than 0.001). Of seven patients with lymph-vascular space invasion who experienced tumor recurrence, five developed extra-pelvic metastases. Discriminant function analysis of these data revealed a statistically significant correlation between lymph-vascular space invasion and tumor recurrence, independent of histologic differentiation of myometrial penetration. These findings suggest that lymph-vascular space invasion by tumor cells is an important prognostic variable in Stage I endometrial cancer which should be considered in treatment planning.

Adenocarcinoma↗