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Results for “Gravity, Altered”

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At least 649 records · Page 36Linked to original sources

PubMed1985

Recirculation model following MCA occlusion in rats. Cerebral blood flow, cerebrovascular permeability, and brain edema.

A new model for establishing a successful and consistent arterial recirculation has been devised following middle cerebral artery (MCA) occlusion in the rat. A snare ligature was introduced at the stem of the MCA just distal to the lenticulostriate branches, and occlusion and recirculation were performed by pulling and releasing the thread. This method had an advantage over the use of a small clip which caused damage to the artery without good recirculation. Study of local cerebral blood flow using carbon-14 (14C)-iodoantipyrine, of cerebrovascular permeability using 14C-aminoisobutyric acid, and of brain-water content using the microgravimetric technique was performed upon recirculation following various periods of occlusion and compared with the results in permanent ischemia. A reactive hyperemia was noted within the previously ischemic area immediately upon recirculation following either a 30-minute or a 2-hour ischemic period. One or 2 hours later, delayed hypoperfusion developed in this region, but the circulation over the periphery of the ischemic area recovered well. Cerebrovascular permeability was not, however, altered during the time courses studied. Topographic changes in tissue specific gravity were compared between permanent and transient ischemia in the corresponding time-courses. Although there was a greater decrease in tissue specific gravity following recirculation when the ischemic period was maintained longer, edema formation was resolved by recirculation. Further study is required to determine thresholds of ischemic brain damage and edema formation at recirculation following focal cerebral ischemia.

Aminoisobutyric Acids↗

PubMed2006

Contact-free measurement of heart rate, respiration rate, and body movements during sleep.

We describe a noncontact method for the ambulant measurement of basic sleep physiology parameters in humans, particularly for field studies involving sleep research and sleep disturbances. This method traces the body movements, respiration, and heart action of a person at rest or asleep on a bed, using four high-resolution force sensors installed under the bedposts. The recoil movement of the body at each heartbeat, known as the cardioballistic effect, as well as the lifting and lowering of the thorax, while breathing, causes very small shifts o f the center of gravity of the bed andthe subject. These shifts arereflected in the altering forcedistributions across the four sensors. Cardiac and respiratory parameters and the subject's movement activity can be calculated from the sensor signals. Neither electrodes nor other kinds of transducers are in direct contact with the subject, which is the main advantage of this technique over conventional methods. Laboratory experiments were carried out to estimate validity and practicability. The method has been found to be adequate, especially for automated and unattended sleep-data collection over long periods of time.

Adult↗

PubMed2002

Hypergravity-induced immunomodulation in a rodent model: lymphocytes and lymphoid organs.

The major goal of this study was to quantify changes in lymphoid organs and cells over time due to centrifugation-induced hypergravity. C57BL/6 mice were exposed to 1, 2 and 3 G and the following assays were performed on days 1, 4, 7, 10, and 21: spleen, thymus, lung, and liver masses; total leukocyte, lymphocyte, monocyte/macrophage, and granulocyte counts; level of splenocyte apoptosis; enumeration of CD3+ T, CD3+/CD4+ T helper, CD3+/CD8+ T cytotoxic, B220+ B, and NK1.1+ natural killer cells; and quantification of cells expressing CD25, CD69, and CD71 activation markers. The data show that increased gravity resulted in decreased body, spleen, thymus, and liver, but not lung, mass. Significant reductions were noted in all three major leukocyte populations (lymphocytes, granulocytes, monocyte/macrophages) [correction of macrphages] with increased gravity; persistent depletion was noted in blood but not spleen. Among the various lymphocyte populations, the CD3+/CD8+ T cells and B220+ B cells were the most affected and NK1.1+ NK cells the least affected. Overall, the changes were most evident during the first week, with a greater influence noted for cells in the spleen. A linear relationship was found between some of the measurements and the level of gravity, especially on day 4. These findings indicate that hypergravity profoundly alters leukocyte number and distribution in a mammalian model and that some aberrations persisted throughout the three weeks of the study. In certain cases, the detected changes were similar to those observed after whole-body irradiation. In future investigations we hope to combine hypergravity with low-dose rate irradiation and immune challenge.

Animals↗

PubMed1990

[The function of the hypophyseal-gonadal system in different variants of glomerulonephritis in children].

A total of 28 children with different varieties of glomerulonephritis were examined for the pituitary-gonadal system (PGS). The examination included measurements of follicle-stimulating and luteinizing hormones, prolactin, estradiol, progesterone and testosterone. To define standards of the content of the hormones under study, 45 children of the control group were examined. The relationship was analyzed between the content of hormones and the disease activity and gravity. The most active phase of glomerulonephritis was characterized by maximal alterations in the content of pituitary and gonadal hormones. The content of the latter ones appeared to be considerably changed in patients with the mixed pattern of glomerulonephritis, attesting to profound functional derangements in the PGS. The intensity of those derangements was determined by the severity of the pathological process.

Adolescent↗

PubMed1985

[Importance of the cytochemical study of blood leukocyte enzyme activity in acute pneumonias].

The authors describe the results of cytochemical study of the activity of alkaline and acid phosphatase, myeloperoxidase and NADP-HH oxidase of neutrophils, acid phosphatase, succinate dehydrogenase and mitochondrial alpha-glycerophosphate dehydrogenases of peripheral blood lymphocytes in 90 patients with acute pneumonia on days 1, 3, 5, 7, 14 and 21 of the disease. It has been shown that changes in the activity of leukocytic enzymes are early and sensitive signs of acute inflammation in the lungs, reflecting the gravity and character of the disease. Some features of the enzymatic alterations depending on the degree of respiratory failure and allergic complications have been disclosed.

Acute Disease↗

PubMed1982

Glucocorticoid receptors and the cell cycle: evidence that the accumulation of glucocorticoid receptors during the S phase of the cell cycle is dependent on ribonucleic acid and protein synthesis.

HeLa S3 cells contain high affinity, saturable protein receptor molecules which steriospecifically bind active glucocorticoids. The number of glucocorticoid receptors per cell changes as cells in culture proceed through the cell cycle (1). HeLa S3 cells brought to the GI/S boundary by the double thymidine block procedure undergo a rapid synchronous round of DNA synthesis when released into thymidine-free medium. Analysis of glucocorticoid receptor binding indicates a rapid rise in cellular receptor number when measurements are made in whole cells at either 3 C (cytoplasmic) or 37 C (nuclear). Cytoplasmic receptors are maintained at levels about 150% above late GI values throughout S and GII phases until mitosis occurs, whereas the nuclear binding of hormone is dramatically reduced during GII and remains low during mitosis and early GI. Similar cell cycle-dependent alterations in receptor number occur in synchronized cell populations obtained by unit gravity sedimentation. Sucrose density gradient analysis and Sephacryl S-200 gel filtration of cytoplasmic receptors during the cell cycle indicate a rapid increase in approximately 7-8S dexamethasone-binding component during early S phase, when receptors accumulate in cells. The role of RNA, protein, and DNA syntheses in mediating this S phase increase in receptor number were next examined. Both cycloheximide and puromycin blocked the increased receptors accumulation that occurs during the S phase, whereas delayed addition of these inhibitors led to partial increases in receptor binding. Several inhibitors of RNA synthesis [actinomycin D, L-521,818-00E10 (Merck), and alpha-amanitin] all effectively inhibited the S phase accumulation of receptor. Increased receptor binding during the S phase was not dependent on DNA replication. These data suggest that the increase in glucocorticoid receptor number during the S phase results from alterations in RNA and protein synthetic processes.

Cell Nucleus↗

PubMed2006

Swimming Paramecium in magnetically simulated enhanced, reduced, and inverted gravity environments.

Earth's gravity exerts relatively weak forces in the range of 10-100 pN directly on cells in biological systems. Nevertheless, it biases the orientation of swimming unicellular organisms, alters bone cell differentiation, and modifies gene expression in renal cells. A number of methods of simulating different strength gravity environments, such as centrifugation, have been applied for researching the underlying mechanisms. Here, we demonstrate a magnetic force-based technique that is unique in its capability to enhance, reduce, and even invert the effective buoyancy of cells and thus simulate hypergravity, hypogravity, and inverted gravity environments. We apply it to Paramecium caudatum, a single-cell protozoan that varies its swimming propulsion depending on its orientation with respect to gravity, g. In these simulated gravities, denoted by f(gm), Paramecium exhibits a linear response up to f(gm) = 5 g, modifying its swimming as it would in the hypergravity of a centrifuge. Moreover, experiments from f(gm) = 0 to -5 g show that the response is symmetric, implying that the regulation of the swimming speed is primarily related to the buoyancy of the cell. The response becomes nonlinear for f(gm) >5 g. At f(gm) = 10 g, many paramecia "stall" (i.e., swim in place against the force), exerting a maximum propulsion force estimated to be 0.7 nN. These findings establish a general technique for applying continuously variable forces to cells or cell populations suitable for exploring their force transduction mechanisms.

Animals↗

PubMed1998

Facilitating survival and recovery by removing autogenic pathology from the clinical picture.

For the most part, the clinical picture is the expression of autogenic pathology and, unless the anatomical insult represents a major structural compromise, it contributes little to the clinical picture. Autogenic pathology created by the processing of peripheral neurological impulses altered by the presence of anatomical insults is created independently of the gravity of the anatomical insults. Even in the presence of a survivable insult, autogenic pathology is often fatal. Each successful resuscitation effort identifies a patient with a survivable insult who almost died before autogenic pathology was removed by cerebral anoxia, and/or electric shock. Similar patients who suffer terminal brain damage cannot be identified. Cardinal receptors furnish the embryo with its first neural contact with its environment. On completion of embryological migration, they occupy a position in the skin overlying the root of their spinal nerve. Cardinal receptors are functionally segmented to the specific distribution of their spinal nerve and use the stable neurological impulses from the skin to furnish the cadence by which peripheral impulses are processed and valued. Selected cardinal receptors may be specifically stimulated by saline infiltration that produces intradermal blebs in the skin overlying their spinal nerve's root. An augmented burst of infiltration pain immediately followed by symptomatic relief identifies monitoring cardinal receptors. The identification of monitoring receptors confirms the presence of pathology found within the specific distribution of their spinal nerve. Peripheral impulses processed within the cadence of highly stimulated cardinal receptors are assigned an insignificant value. Assigning an insignificant value to peripheral impulses altered by the presence of an anatomical insult removes autogenic pathology from the clinical picture. The immediate onset of profound symptomatic relief heralds the removal of autogenic pathology. Visceral pathology is monitored by bilateral pairs of cardinal receptors so it produces discomfort perceived without specific location information. Therefore, the specific visceral distribution has been discounted and is virtually unknown. However, when visceral pathology is correlated with bilateral pairs of monitoring cardinal receptors there are no patient variations.

Aged↗

PubMed2000

[The cell as a gravity-dependent biomechanic system].

In the period of 1995-1997 experimental and theoretical studies with various biomechanic objects, i.e. individual cells and cell associations, were performed under changed gravity (0.00001-5 g). Experimental investigations were conducted using clinostats and centrifuges to model effects of hypo- and hypergravity, and aboard space vehicles in real microgravity. Cell cultures in vitro including fibroblasts and osteoblasts on a solid glass or plastic substrate served as objects of the studies. Changes in value and direction of the gravity vector were found to modify the morphophysiological characteristics of cells: structural organization (spatial rearrangement of the intracell component, changes in forms, sizes and quantity of cells) and functional activity (alterations in energy expenditure and intensity of intracellular metabolism). The data suggest that there should be mechanisms of gravitational sensitivity in living systems on the cellular level. As was stated, sensitivity of unicellular free-living organisms to gravity is mostly defined by the motor activity determined by the level of general metabolism. Morphological characteristics (form, size and mass) are of secondary importance. Theoretical analysis resulted in correction of one of the principle postulates of gravitational biology stating a direct link between size (mass) and gravitational sensitivity of organism. Described were consistent patterns of growth, development, and behavior of unicellular cultures in gravitational fields. Strengthening of the force of gravity (hypergravity) leads to eventual deceleration of cell growth and diminution of biomass gain. On the other hand, the spaceflight environment (microgravity) stimulates growth mechanisms. In our opinion, behind these gravitational effects are altered levels of energy spent by cells to overcome the force of gravity. Opposite trends were observed in experiments with cell cultures in vitro. During space microgravity, fibroblast cultures on the solid substrate decreased the growth rate, and inhibited cell division and migration within the substrate. Compared to the Earth's gravity, under elevated gravity these parameters were noticeably higher. It was demonstrated that the main cause of the unfavorable effects of space microgravity on the cellular level is decay in the adherence of cells to the substrate. Explored were also the most probable mechanisms of the effects of changed gravity on the cell as a biomechanic structure. Specialized and non-specialized graviceptors of various types of cells were crypt-analyzed and classified. In future, investigations should be angled for elucidation of the role of intracellular components in perception and implementation of the gravitational stimulus, and description of quantitative characteristics of energy exchange and metabolism in cells as a function of gravity force and direction.

Biomechanical Phenomena↗

PubMed2003

Studies on vestibular organs in the fry of mutant Medaka.

We provide an overview of the features of vestibular organs, especially of otolith organs in mutant Medaka ha. The ha fish have a dysfunction in sensing gravity due to the absence of utricular otoliths either unilaterally or bilaterally. Especially in their early developmental stages, the posture control is predominantly depend on light rather than on gravity seen in the wild-type. The ha juveniles that were kept and tolerated in an environment with altered light directions indicated a strong light dependency on the posture maintenance, while the fish under an ordinary light environment gradually changed their posture control by sensing light to gravity around 30 days after hatching and beyond. Their behavior under microgravity agreed with such phenomena observed in ground laboratory.

Animals↗

PubMed2005

Effects of spaceflight on postnatal development of arterial baroreceptor reflex in rats.

AIM: It has been reported that spaceflight attenuates the arterial baroreceptor reflex. As this reflex function changes dramatically during postnatal development, we hypothesized that space flight depresses the developmental changes of the reflex system. To test this hypothesis, we evaluated the baroreceptor reflex function in rats, which were exposed to a microgravity environment on a space shuttle 9-25 days after birth. METHODS: Baroreceptor reflex sensitivity and the afferent sensitivity were evaluated by measuring heart rate (HR) and aortic nerve activity (ANA) changes in response to an increase in mean arterial pressure (MBP) derived by phenylephrine injection (20-50 microg kg(-1)) under urethane-anaesthesia. RESULTS: Baroreceptor reflex sensitivity (% change of HR/% change of MBP) was lower in the flight group (FLT: -0.19 +/- 0.04, n = 4) than either the asynchronous ground control group (AGC: -0.47 +/- 0.06, n = 6, P < 0.01) or the vivarium group (VIV: -0.41 +/- 0.07, n = 6, P < 0.05). This was similar to the differences of the afferent sensitivity (% change of ANA/% change of MBP) between FLT (2.07 +/- 0.30) and the control groups (AGC: 2.71 +/- 0.22, n.s.; VIV: 3.00 +/- 0.32, P < 0.05). At the end of 30 days of recovery under normal gravity conditions, however, there were no significant group differences in these parameters. conclusion: These results suggest that the space environment attenuates the postnatal development of the arterial baroreceptor reflex function in rats, which may be partially because of a depression of the postnatal development of the baroreceptor afferents. These functional alterations, however, recover to their normal level on re-exposure to the Earth's gravity.

Animals↗

PubMed1993

The altered gravitropic response of the lazy-2 mutant of tomato is phytochrome regulated.

Shoots of the lazy-2 (lz-2) gravitropic mutant of tomato (Lycopersicon esculentum Mill.) have a normal gravitropic response when grown in the dark, but grow downward in response to gravity when grown in the light. Experiments were undertaken to investigate the nature of the light induction of the downward growth of lz-2 shoots. Red light was effective at causing downward growth of hypocotyls of lz-2 seedlings, whereas treatment with blue light did not alter the dark-grown (wild-type) gravity response. Downward growth of lz-2 seedlings is greatest 16 h after a 1-h red light irradiation, after which the seedlings begin to revert to the dark-grown phenotype. lz-2 seedlings irradiated with a far-red light pulse immediately after a red light pulse exhibited no downward growth. However, continuous red or far-red light both resulted in downward growth of lz-2 seedlings. Thus, the light induction of downward growth of lz-2 appears to involve the photoreceptor phytochrome. Fluence-response experiments indicate that the induction of downward growth of lz-2 by red light is a low-fluence phytochrome response, with a possible high-irradiance response component.

Darkness↗

PubMed2001

Brain sources of EEG gamma frequency during volitionally meditation-induced, altered states of consciousness, and experience of the self.

Multichannel EEG of an advanced meditator was recorded during four different, repeated meditations. Locations of intracerebral source gravity centers as well as Low Resolution Electromagnetic Tomography (LORETA) functional images of the EEG 'gamma' (35-44 Hz) frequency band activity differed significantly between meditations. Thus, during volitionally self-initiated, altered states of consciousness that were associated with different subjective meditation states, different brain neuronal populations were active. The brain areas predominantly involved during the self-induced meditation states aiming at visualization (right posterior) and verbalization (left central) agreed with known brain functional neuroanatomy. The brain areas involved in the self-induced, meditational dissolution and reconstitution of the experience of the self (right fronto-temporal) are discussed in the context of neural substrates implicated in normal self-representation and reality testing, as well as in depersonalization disorders and detachment from self after brain lesions.

Brain Mapping↗

PubMed1992

Identification of specific gravity sensitive signal transduction pathways in human A431 carcinoma cells.

Epidermal growth factor (EGF) activates a well characterized signal transduction cascade in human A431 epidermoid carcinoma cells. The influence of gravity on EGF-induced EGF-receptor clustering and early gene expression as well as on actin polymerization and actin organization have been investigated. Different signalling pathways induced by the agents TPA, forskolin and A23187 that activate gene expression were tested for sensitivity to gravity. EGF-induced c-fos and c-jun expression were decreased in microgravity. However, constitutive beta-2 microglobulin expression remained unaltered. Under simulated weightlessness conditions EGF- and TPA-induced c-fos expression was decreased, while forskolin- and A23187-induced c-fos expression was independent of the gravity conditions. These results suggest that gravity affects specific signalling pathways. Preliminary results indicate the EGF-induced EGF-receptor clustering remained unaltered irrespective of the gravity conditions. Furthermore, the relative filamentous actin content of steady state A431 cells was enhanced under microgravity conditions and actin filament organization was altered. Under simulated weightlessness actin filament organization in steady state cells as well as in EGF-treated cells was altered as compared to the 1 G reference experiment. Interestingly the microtubule and keratin organization in untreated cells showed no difference with the normal gravity samples. This indicates that gravity may affect specific components of the signal transduction circuitry.

Calcimycin↗

PubMed1989

[Disorders of cardiac rhythm in children with pre- and perinatal damage of the brain].

Alterations in the cardiac rhythm were analyzed in 108 children with pre- and perinatal hypoxic-traumatic brain injuries. Comparisons were made with the data obtained in a group of 30 normal children. The data of the clinical and electrophysiological assessment of the encephalopathy gravity were correlated with the regularity of the cardiac rhythm: heart rate (HR), mode (M), mode amplitude (MA), variation swing (VS), tension index (TI) according to R. M. Baevsky and redundancy coefficient (RC). It has been established that the encephalopathic children demonstrated an increase in the HR, TI and MA and a fall of the M and VS. The intensity of the alterations under study correlated well with the gravity of pre- and perinatal brain injuries. The TI, MA and R were of the highest diagnostic value. Taking into consideration of the magnitude of cardiac rhythm alterations one can predict neurological sequelae detectable in children aged 2 years.

Arrhythmias, Cardiac↗

PubMed1992

Lidocaine 0.5% spinal anaesthesia: a hypobaric solution for short-stay perirectal surgery.

The efficacy of subarachnoid injection of 8 ml lidocaine 0.5% was assessed in ten outpatients having perirectal surgery in the jackknife position. This solution is hypobaric, with a baricity 0.9985 +/- 0.0003 (mean +/- SD). Injections were made with the patient in the surgical position (with the upper torso at a 15 degrees downward inclination). Sensory level was tested by pinprick. Times to two-segment regression, to complete resolution of sensory analgesia, to urination, and to discharge from the recovery room were recorded. All injections produced effective anaesthesia for surgery. Lidocaine 0.5% behaves clinically as a hypobaric solution. Dermatomal levels remained low (T11 to L5) while the patients were in the surgical position (head down), but rose two to six dermatomes if the patient's head was elevated after surgery. Time to two-segment regression was 97 +/- 36 min, time until regression to S1 was 116 +/- 22 min, time to complete resolution of sensory blockade was 151 +/- 23 min, time to urination was 197 +/- 64 min, and time to discharge from the recovery room was 205 +/- 45 min. Lidocaine 0.5% provides effective spinal anaesthesia of short duration appropriate for outpatient surgical procedures. Dermatomal sensory spread of anaesthesia, and our measurements of specific gravity, indicate that this solution is hypobaric. It appears that changes in position can alter the spread of analgesia for at least one hour after injection and, thus, we caution against elevating the patient's head in the immediate postoperative period.

Adult↗

PubMed1988

Effects of bromocriptine on prolactin cellular hypertrophy, proliferation and secretory activity in diethylstilbestrol-induced pituitary tumors.

Pituitary tumors induced by chronic diethylstilbestrol (DES) treatment in female F344 rats were treated subsequently with bromocriptine (BC). Effects of BC on separable subpopulations of lactotrophs were examined. Enzymatically dissociated cells from individual pituitaries were assessed regarding total number, relative lactotroph population, intracellular prolactin (PRL) content, PRL release in primary culture, and density alterations by separation in Ficoll-Hypaque or after sedimentation at unit gravity. In addition to the treatment and analysis of in situ tumors, the effects of BC treatment in vitro were assessed, using tumor cells which were first separated on Ficoll-Hypaque. Cell proliferation was assessed by cell cycle analysis, using DNA measurement by laser flow cytometry. BC treatment of tumors reversed the effects of DES on pituitary weight, PRL content and in vitro PRL release. Total cell recovery was not affected by BC, but cell separation showed that BC reduced the number of larger PRL-containing cells. Cell cycle analysis showed a decrease in numbers of cells in S and G2 cycle phases after BC in only one of four experiments. BC had an effect on proliferation in only the upper gradient fractions, containing the smallest cells. Culture of Ficoll-separated tumor cells revealed greater PRL release among lighter/smaller cells. BC treatment inhibited PRL release from both light and dense cells. The results establish that PRL cell hypertrophy, as well as hyperplasia, results from DES treatment. Bromocriptine treatment reverses this hypertrophy concomitant with inhibiting PRL synthesis and release. Reversal of proliferation in tumor cells is not a major effect of bromocriptine treatment.

Animals↗

PubMed1986

[Incidence of microangiopathy in insulin-dependent diabetes mellitus (data from the morphological examination of skin biopsy specimens)].

The biopsies of the thigh skin from 85 patients with insulin-dependent (juvenile) diabetes mellitus are studied. Diabetic microangiopathy is detected histologically in 70 patients. The degree of microangiopathy was positively correlated with the duration of diabetes (p less than 0.01) and this allowed to calculate the probability of vascular alterations development at various periods of disease. The patient age and the gravity of insulin-dependent diabetes did not influence significantly the frequency and the degree of diabetic microangiopathy (p greater than 0.05).

Adolescent↗