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Results for “GRAVITY”

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At least 865 records · Page 48Linked to original sources

PubMed1987

Infusion phlebitis associated with a programmable syringe-pump system versus gravity-feed minibottles.

The occurrence of infusion phlebitis in patients receiving intravenous antibiotics via a gravity-feed minibottle system versus a new syringe-pump system was compared. Patients at least 18 years old who had indwelling intermittent injection sites inserted for medication administration were randomized to either the minibottle system or the syringe-pump system. Antibiotics in minibottles were diluted in 50-100 mL of 5% dextrose injection; in the syringe-pump group, aminoglycoside antibiotics were diluted in 0.9% sodium chloride injection and all other antibiotics were diluted in sterile water for injection. Antibiotics were not piggybacked into running primary infusions in any of the study patients, and no other medications except for 0.9% sodium chloride flushes were administered through the catheters. All catheters were inserted in peripheral veins and evaluated for phlebitis by i.v. nurse specialists using standardized criteria. Catheters were changed upon the occurrence of grade 1 phlebitis or after a period of three days without the development of phlebitis. Over an 18-week period, 85 catheter sites (53 syringe-pump group versus 32 minibottle group) were evaluated in 30 patients (14 syringe-pump group versus 16 minibottle group). The mean +/- S.D. catheter life in both groups was 50.6 +/- 20 hours. Phlebitis occurred in 62% of syringe-group sites versus 66% of minibottle-group sites; the incidence and severity of phlebitis were not significantly different between groups. The majority of catheter sites were infused with cefazolin sodium. The potential for phlebitis using the syringe-pump system in this study appears to be similar to that of the gravity-feed minibottle system when appropriate diluents, diluent volumes, and infusion rates are used.

Adult↗

PubMed1986

Relationship between movements of the head and the center of gravity of the body in Menière's disease.

The body sway of the patients with unilateral and bilateral Ménière's disease was recorded by using a cephalograph and a stabilometer, and analyzed with a microcomputer. The results show that the locus type, locus area and locus length traced by the head's center and the body's center of gravity are useful parameters of the body sway, representing the characteristics of peripheral vestibular disorders. The noteworthy characteristics are shown in the right-and-left type and forward-and-backward type in statokinesigram, in the significant differences of locus area and/or locus length between the head movement and the movement of the center of gravity, and the change of the averaged divisional frequencies of the body sway with eye-closing.

Dominance, Cerebral↗

PubMed1979

Ultrastructural peculiarities of the chemical transmission of the nerve impulse in the gravity receptors of some invertebrates.

Electron microscopic and cytochemical studies of the synapses of the gravity receptors in Coelenterata, Ctenophora, Annelids and Molluscs has shown the mediators both of cholinergic and adrenergic systems. As a rule, the two mediatros were connected with different receptor systems (Ctenophora) or with the synaptic structures of various parts of the chain: receptor--neuron--effector (Medusa, Annelids). The synaptic transmission in the gravity receptor of studied molluscs classes is carried out by means of either cholinergic or adrenergic systems.

Adrenergic Fibers↗

PubMed1985

Retinal tear associated with gravity boot use.

A case of retinal tear without detachment is presented that is presumed to be associated with use of a gravity guidance system--"gravity boots." Such an occurrence has not been previously reported.

Adult↗

PubMed1978

Nonlinear behavior of sitting humans under increasing gravity.

To determine the nonlinear properties of the upright sitting human body, driving-point impedance as well as the transmissibility from seat to head were determined under increased gravity on a centrifuge. Under this condition a shift of resonances to higher frequencies was observed. At the same time the transmissibility increased distinctly. To explain this behaviour with a model, a nonlinear multi-degree-of freedom model of the upright sitting body was calculated. It elements represent identifiable body parts. Protective measures for normal gravity conditions, as well as for sustained acceleration, were derived.

Acceleration↗

PubMed1982

[Use of an electronic gravity infusion regulator for infusion therapy in routine conditions. Comparative clinical study].

In comparison with the ordinary roller clamp the gravity-infusion controller allows a significant lowering of complications and start-ups at peripheral venous access sites. These results are effectively based on a decrease in the infiltration rate of about 30%. For approximately 80% of the remaining complications an early alarm and interruption of the infusion takes place. It is of importance that the electronic controller avoids the excessive variations of the drop rate found with roller clamps. In contrast to these advantages problems may arise under certain circumstances caused by the narrowing of the control range based on the limited available hydrostatic pressure. Application of the electronic gravity controller must be seen primarily for peripheral venous access sites. Its use is particularly advantageous where an infiltration of the infusion solution results in an endangering of the patient (cytostatic agents, strong alkaline solutions, for instance NaHCO3, potassium concentrates, medication additions, for instance vasoconstricting agents). In addition, it makes sense to use the controller in situations where the accuracy of an infusion regulated by a roller clamp is considered to be inadequate.

Bicarbonates↗

PubMedDate not supplied

Current status of the problem of the mechanism of gravity reception in plants.

Basic work carried out recently on the role of the structural-functional condition of cell organelles in the development of geotropic reaction in higher plants is reviewed. On the basis of analysis of theoretical proposals and experimental investigations of the molecular mechanism of perception and realization of the gravity stimulus, a hypothesis was developed that the key factor in the development of geotropic reaction is an interaction of cell organelles with membranes of the endoplasmic reticulum as a result of their sensing the gravity stimulus.

Aerobiosis↗

PubMedDate not supplied

[Gravity and animal development].

Based on the literature data and the author's findings, a comparative-and-physiological analysis of the responses of the animals of a different evolutionary level to micro- and hypergravity has been attempted. The experimental data accumulated by this time show a good fit to N.N.Sirotinin's concept about an evolution of the resistance and the reactivity: the high tolerance to a changed gravity in the insects, the presence of reaction in fish and amphibians mainly in most early developmental stages or in reduced (having high sensitivity) lay, a wide range of the responses to a changed gravity in birds and mammals. The investigative prospects in the field of gravitational biology of the development are discussed.

Adaptation, Physiological↗

PubMed1994

Human vertical optokinetic nystagmus and after-response, and their dependence upon head orientation with respect to gravity.

Characteristics of human vertical optokinetic nystagmus (VOKN) and afternystagmus (VOKAN) were examined by electro-oculography in 18 normal human subjects by means of the analysis of slow phase velocity (SPV) and area under the regression curve of the VOKAN decay. Under normal gravity, subjects were tested in upright and left ear down (90 degrees roll) positions, respectively, using a hemisphere onto which stripes were projected at a velocity of 40 degrees/s in left, right, up and down directions. Analysis of the VOKN and VOKAN revealed a significant asymmetry of vertical eye movements in the subjects' sagittal plane, ie, stronger upward SPV than downward in both VOKN and VOKAN decay. This asymmetry became even more prominent when the head was in the 90 degrees roll position. It is postulated that the asymmetry of VOKN and VOKAN in humans, as in animals, is due to the asymmetrical storage capability of the vertical velocity storage mechanism which mainly contributes to upward eye movements. In addition, it is postulated that the vertical storage mechanism is modified by the action of gravity on the otolith organs. However, only two out of our 18 subjects demonstrated cross-coupling, as reported in animals, from the horizontal to the vertical mode of storage when the head was tilted away from the spatial vertical.

Adult↗

PubMed1993

Simulating reduced gravity: a review of biomechanical issues pertaining to human locomotion.

In the decade preceding Apollo missions to the Moon, extensive studies were conducted on human locomotion in reduced gravity. These investigations focused primarily on issues of maneuverability and energy expenditure and not on musculoskeletal loading, which is of more interest to planners of long-duration space missions. The techniques have included water immersion, parabolic aircraft flights, supine and erect cable suspension and centrifugal methods. The practical implications of the findings from these studies are: 1) the present shuttle treadmill running surface would not suffice if one wanted to run with a natural style at levels greater than 0.6 G; 2) in terms of attempting to replicate typical ground reaction force profiles during locomotor exercise at reduced gravity levels, it appears as though it is easier to match the peak rates of change of force (maxDFDT) than it is to match values for the peak force magnitudes (maxGRF).

Biomechanical Phenomena↗

PubMed1993

Mechanism of gravity-dependent atelectasis. Analysis by nonradioactive xenon-enhanced dynamic computed tomography.

RATIONALE AND OBJECTIVES: The physiologic mechanism of gravity-dependent atelectasis (GDA), a common finding identified during anesthesia, is not well understood. The purpose of this study was to determine whether an inherent reduction in alveolar volume or a reduction in alveolar ventilation is the more important causative factor for the development of GDA in an experimental animal model. METHODS: After uniform reduction of lung volume in ten rabbits by artificially induced pneumoperitoneum, dynamic inhalation computed tomography (CT) was performed using 50% nonradioactive xenon in oxygen. Time-CT attenuation value curves were fitted to an exponential function, CT value = a - b x e(-kt), and K value, which is proportional to the alveolar ventilation/alveolar volume ratio, was calculated by regression analysis. RESULTS: Gravity-dependent atelectasis occurred only in 5 of 10 rabbits. In this group, K values in the dorsal regions increased before the appearance of GDA. No significant change in K values in the ventral regions was observed. CONCLUSION: One mechanism of GDA may be a preferential reduction in alveolar volume without small airway collapse rather than alveolar volume loss secondary to decreased ventilation.

Animals↗

PubMed1993

Diuresis renography. The need for an additional view after gravity-assisted drainage.

The role of diuresis renography (DR) in the evaluation of pelvi-ureteric junction obstruction is well established. However, problems may be encountered when applying this technique to patients after pyeloplasty because of the role of gravity-assisted drainage (GAD) in this post-operative group. Twenty-three radionuclide studies that were performed in 21 children were reviewed. All children underwent standard DR and all then had an additional view performed after GAD. In 12 children evaluated in a preoperative assessment for possible obstruction, 5 were obstructed on both DR and after GAD, 1 was equivocal on DR but drained after GAD, and 6 were not obstructed in either part of the study. In 11 children assessed after pyeloplasty, 5 were obstructed on DR but not obstructed on GAD, 3 were not obstructed in both studies, 1 was obstructed in both, and 2 were equivocal on DR but not obstructed after GAD. It can be concluded that when assessing patients, particularly those who have undergone pyeloplasty, DR should be supplemented with an additional view acquired after gravity-assisted drainage.

Child, Preschool↗

PubMedDate not supplied

Gravity, blood circulation, and the adaptation of form and function in lower vertebrates.

Gravitational force influences musculoskeletal systems, fluid distribution, and hydrodynamics of the circulation, especially in larger terrestrial vertebrates. The disturbance to hydrodynamics and distribution of body fluids relates largely to the effects of hydrostatic pressure gradients acting in vertical blood columns. These, in turn, are linked to the evolution of adaptive countermeasures involving modifications of structure and function. Comparative studies of snakes suggest there are four generalizations concerning adaptive countermeasures to gravity stress that seem relevant to lower vertebrates generally. First, increasing levels of regulated arterial blood pressure are expected to evolve with some relation to gravitational stresses incurred by the effects of height and posture on vertical blood columns above the heart. Second, aspects of gross anatomical organization are expected to evolve in relation to gravitational influence incurred by habitat and behavior. Third, natural selection coupled to gravitational stresses has favored morphological features that reduce the compliance of perivascular tissues and provide an anatomical "antigravity suit." Fourth, natural selection has produced gradients or regional differences of vascular characteristics in tall or elongated vertebrates that are active in high gravity stress environments. Consideration or awareness of these principles should be incorporated into interpretations of structure and function in lower vertebrates.

Adaptation, Physiological↗

PubMed1996

Comparative electronmicroscopical investigations on the influences of altered gravity on cytochrome oxidase in the inner ear of fish: a spaceflight study.

The regional metabolic activity in the otolithic sensory epithelia of the inner ear of a cichlid fish (Oreochromis mossambicus) was investigated on light- and electronmicroscopical level using the cytochemical method for detection of cytochrome oxidase activity. In adult animals a characteristic distribution of mitochondria with high enzyme activity was found in sensory and non-sensory cells of otolithic sensory epithelia, which was correlated with regions with a high energy demand. These findings were the basis for studies on the influence of long-term altered gravity conditions in developing larvae: hypogravity (10(-4) g in spaceflight), normal gravity (1 g in a centrifuge in space and 1 g on earth) and hypergravity (3 g in a laboratory centrifuge). Cytochrome oxidase activity was quantified in different parts of the sensory hair cell synapse in the vestibular sensory epithelia utricle and saccule: apical and basal cytoplasm, postsynaptic area of the afferent synapse and presynaptic region of the efferent synapse. Our results show that the energy metabolism of utricle, but not of saccule is decreased after microgravity exposure during the 2nd German Spacelab Mission D-2. However, a general effect of the spaceflight is detectable in both sensory epithelia. Long-term exposure to increased acceleration (3 g) had no effects on cytochrome oxidase activity in inner ear sensory epithelia.

Animals↗

PubMed1996

Neurologic decompression illness: a gravity score.

Treatment of neurologic decompression accidents consists of various hyperbaric oxygen (HBO) protocols. To facilitate such comparisons between different protocols we developed a gravity score. A group of 96 divers was used to establish the score. On admission we first identified signs and symptoms that had possible predictive value (chi 2 test). The parameters included were repetitive dive, clinical course before HBO, objective sensory disorder, motor impairment, and urinary disturbances. Each parameter was assigned a coefficient. The sum of the coefficients for each accident, based on the most severe manifestations before decompression therapy, yielded a score for each diver. A multivariate analysis was used to evaluate the overall agreement between the model prediction and clinical observations, which was 78.7%. A second group (66 divers) was used to validate the score; this group showed a significant difference in the gravity score between the divers who had sequelae and those who did not (P = 0.0001), and between the divers who had incapacitating sequelae and those who had mild sequelae (P = 0.04). Eighty-six percent of the divers with a score above 7 developed sequelae. This index remains to be validated in a prospective multicenter study. If endorsed, valid comparisons can be made between the different therapeutic protocols.

Adult↗

PubMedDate not supplied

[Effect on water metabolism of body posture relative to the gravity vector].

A combined effect of hypokinesia and body position at different angles to the gravity vector on the water content and rate of its metabolism was studied. It was shown that bed rest reduced total water losses and the rate of its metabolism. It was body position as related to the gravity vector rather than bed rest that influenced the total water content in the body.

Adult↗

PubMed2026

Yeast Strain Development and Process Intensification in High-Gravity Fermentation.

High- and very-high-gravity (HG/VHG) fermentation increases substrate loading and product titers, thereby improving fermenter utilisation and potentially reducing water use and downstream processing requirements. Initially developed for brewing and fuel ethanol production, these approaches are now applied more broadly in food, beverage, and bioproduct manufacturing. This MiniReview summarises operational definitions and industrial drivers of HG/VHG fermentation and examines the associated constraints in rheology, mass and heat transfer, osmotic and ethanol stress, nutrient availability, and oxidative damage. Yeast improvement strategies are reviewed, including adaptive laboratory evolution, mutagenesis, genome shuffling, multiplex genome editing, non-conventional yeasts, and multi-omics-guided selection. Process developments such as no-cook simultaneous liquefaction, saccharification and fermentation (SLSF), enzyme formulation, nutrient management, and in situ product recovery are considered together with applications in alcoholic beverages, organic acids, microbial lipids, and other value-added products. The review also discusses coproduct valorisation and the need to integrate strain development with process design. Current evidence supports HG/VHG fermentation as a useful process-intensification platform, although performance and sustainability depend strongly on feedstock, operating conditions, product requirements, and the basis used to report fermentation outcomes.

circular bioeconomy↗

PubMed2001

[Influence of gravity change on EGF-induced signal transduction].

With the development of aerospace technology, biological effects induced by alteration of gravitation are drawing more and more attention. Among them the influence of alteration of gravitation on cytokine-induced signal transduction has been well studied recently. Epidermal growth factor (EGF)-induced signal transduction can activate increase of cell proliferation in most cell types, so it is always a hotspot in these years. Among the early effects evoked by EGF are receptor clustering, cell rounding, and early gene expression. After the study about the induction of EGF on human A431 cell line, it was observed that EGF-induced c-fos and c-jun expression decreased in microgravity. This was caused by alteration of the EGF receptor and protein kinase C-mediated signal transduction pathways. Meanwhile the key component of cytoskeleton, the actin microfilament system, was found to be linked to the EGF-induced signal transduction cascades either. So it seems reasonable to suggest that the cytoskeleton constitutes the gravity-sensitive cell component.

Actin Cytoskeleton↗