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PubMed2002

Human muscle sympathetic nerve activity and plasma noradrenaline kinetics in space.

Astronauts returning from space have reduced red blood cell masses, hypovolaemia and orthostatic intolerance, marked by greater cardio-acceleration during standing than before spaceflight, and in some, orthostatic hypotension and presyncope. Adaptation of the sympathetic nervous system occurring during spaceflight may be responsible for these postflight alterations. We tested the hypotheses that exposure to microgravity reduces sympathetic neural outflow and impairs sympathetic neural responses to orthostatic stress. We measured heart rate, photoplethysmographic finger arterial pressure, peroneal nerve muscle sympathetic activity and plasma noradrenaline spillover and clearance, in male astronauts before, during (flight day 12 or 13) and after the 16 day Neurolab space shuttle mission. Measurements were made during supine rest and orthostatic stress, as simulated on Earth and in space by 7 min periods of 15 and 30 mmHg lower body suction. Mean (+/- S.E.M.) heart rates before lower body suction were similar pre-flight and in flight. Heart rate responses to -30 mmHg were greater in flight (from 56 +/- 4 to 72 +/- 4 beats min(-1)) than pre-flight (from 56 +/- 4 at rest to 62 +/- 4 beats min(-1), P < 0.05). Noradrenaline spillover and clearance were increased from pre-flight levels during baseline periods and during lower body suction, both in flight (n = 3) and on post-flight days 1 or 2 (n = 5, P < 0.05). In-flight baseline sympathetic nerve activity was increased above pre-flight levels (by 10-33 %) in the same three subjects in whom noradrenaline spillover and clearance were increased. The sympathetic response to 30 mmHg lower body suction was at pre-flight levels or higher in each subject (35 pre-flight vs. 40 bursts min(-1) in flight). No astronaut experienced presyncope during lower body suction in space (or during upright tilt following the Neurolab mission). We conclude that in space, baseline sympathetic neural outflow is increased moderately and sympathetic responses to lower body suction are exaggerated. Therefore, notwithstanding hypovolaemia, astronauts respond normally to simulated orthostatic stress and are able to maintain their arterial pressures at normal levels.

Adult↗

PubMed2002

Measurement of the subarachnoid space by ultrasound in preterm infants.

BACKGROUND: Measurements of the subarachnoid space during routine cranial sonography may provide an indirect method of monitoring brain growth in preterm infants. METHODS: The width of the subarachnoid space was measured on coronal views during head sonography. Initial scans (within five days of birth) were compared with follow up scans. RESULTS: A total of 361 scans were performed on 201 preterm infants. The mean width of the subarachnoid space was < 3.5 mm for 95% of initial scans. It was slightly larger in neonates born closer to term, the equivalent of an increase of 0.02 mm/gestational week (95% confidence interval 0 to 0.10 mm) for initial scans. When the scans of all infants, born at 24-36 gestational weeks who were 36 weeks corrected gestational age were compared, the mean (SD) subarachnoid space was 60% larger for follow up scans than for initial scans: 3.2 (1.38) v 1.95 (1.35) mm (p = 0.002) or the equivalent of a mean increase of 0.20 mm/week (95% confidence interval 0.15 to 0.30 mm) for follow up scans. At 36 weeks corrected gestational age, mean head circumference was not different between those having initial or follow up scans (33.0 (2.0) v 32.2 (1.9) cm; p = 0.31). CONCLUSION: The mean subarachnoid space is normally < 3.5 mm in preterm infants. The difference between initial and follow up scans suggests reduced brain growth in extrauterine preterm babies.

Cephalometry↗

PubMed1991

Early orientation of attention toward the half space ipsilateral to the lesion in patients with unilateral brain damage.

Posner has suggested that unilateral spatial neglect could be due to a difficulty in disengaging attention from its current focus to orient it toward the neglected half space. Clinical and experimental data suggest, however, that this disengaging difficulty could be only one aspect of a more complex disturbance also characterized by an early automatic orienting of attention toward the half space ipsilateral to the lesion. To test this hypothesis, two different investigations in unselected groups of patients with right and left brain-damage were carried out. The first investigation, to evaluate forms of lateral orienting of attention severe enough to provoke an overt gaze deviation, consisted of the systematic assessment of the phenomenon of "magnetic gaze attraction". The second investigation, to detect milder forms of automatic orienting of attention, analysed the temporal sequence followed in identifying the pictures represented in an "Overlapping Figures task", to see if patients tended to identify first figures lying in the half space ipsilateral to the lesion. In both investigations results consistently showed: a) that patients with right brain damage tend to orient attention automatically toward the ipsilateral half space more than patients with left brain damage; b) that this tendency is tightly linked to the presence of behavioural manifestations of hemi-neglect. These results are therefore consistent with the hypothesis that hemi-neglect is a multi-component syndrome with an early orienting of attention toward the half space ipsilateral to the lesion as the first of these components.

Analysis of Variance↗

PubMed1986

Renal fascial pathway: posterior extension of pancreatic effusions within the anterior pararenal space.

Retrorenal extension of pancreatic effusion or phlegmon associated with pancreatitis has been described frequently and is generally considered to represent extension of these processes from the anterior into the posterior pararenal space. A series of meticulous cadaveric dissections (n = 8) and a review of a large number of patients with pancreatitis (n = 53) show that these posterior collections actually represent extension of pancreatitis from the anterior pararenal space to a potential space between the laminae of the posterior renal fascia. Of 40 patients with posterior extension of pancreatic effusion or phlegmon, interfascial involvement was observed in all 40 and was bilateral in nine (23%). True involvement of the posterior pararenal space was uncommon, as was extension into the perirenal space. This phenomenon appears as a continuum of the well-described thickening of the renal fascia secondary to pancreatitis. It can be explained by new observations of the relationships between the fascia of Gerota and the lateroconal fascia.

Cadaver↗

PubMed1980

Relation between respiratory valve dead space and tidal volume.

We measured the "effective" dead space of five commonly used respiratory valves: Hans Rudolph valve, two-way J valve, triple-J valve, and modified Otis-McKerrow valves without and with vane. The dead space was measured using a technique that mimicked the operation of valves during ordinary laboratory procedures. The valves were ventilated with tidal volumes ranging from 0.35-3.00 liters and at different frequencies. With all valves, there was a marked tendency for "effective" dead space to be tidal volume dependent. The measured dead space approached the water-displacement volume of the common chamber of the valve only at tidal volumes in excess of 2.0 liters. The relation between valve dead space and tidal volume was independent of frequency.

Mathematics↗

PubMed1981

Measurement of dead space ventilation using a pHa servo-controlled ventilator.

A control system for the systemic arterial pH (pHa) servo control of mechanical ventilation has recently been developed. If pHa is maintained constant by the change, separation of minute volume into alveolar ventilation and physiological dead space ventilation (VE = fVA VDp) can be manipulated to show that VDp = (VE1 - VE 2)/(f1 - fe) where f1 and f2 are different ventilator frequencies and VE1 and VE2 are expired minute volumes at these frequencies. Also, added dead space can be measured. VDadded = (VE2 - VE1)/f where VE1 and VE2 are the minute volumes before and after the dead space was added. The validity of these equations was tested in the anesthetized dog. The measured added dead space was in close agreement with the volume of dead space which was added and with that measured by another independent method. The measurement of VDp, probably as a result of tidal volume-related changes in VDp, did not agree as well with VDp measured by an independent method.

Animals↗

PubMed1985

Pleural space thickness in situ by light microscopy in five mammalian species.

The thickness of the pleural space was measured by a focusing method using a light microscope (X157, 2.5-micron depth of focus). In anesthetized animals, thin transparent parietal pleural windows were made by dissection of intercostal muscle. Multiple postmortem measurements were made of the combined thickness of the pleural space and the window by focusing in sequence on the lung surface and on 1- to 2-micron tantulum particles sprayed on the window. The window thickness was measured after creating a pneumothorax and retracting the lungs. In supine rabbits the pleural space measured at various heights on the costal surface was of uniform thickness (16 micron) except for a thicker region (62 micron) located within 3 mm of the most dependent part of the lung. The thicker region reverted to the uniform thickness after it was placed in a nondependent position by inverting the animal from the supine to prone position, indicating fluid drainage by gravity. In the prone position near midchest, pleural space thickness (t) averaged 6.9 micron in the mouse, 10.2 in the rat, 17.2 in the rabbit, 18.3 in the cat, and 23.6 in the dog. Animals of larger body mass (M, kg) had a wider pleural space: t = 13.1 X M0.20. There was no contact between the two pleurae, indicating that fluid lubrication facilitates sliding between the lung and chest wall. Based on the t vs. M relationship and estimates of the viscous flow of pleural liquid, pleural fluid exchange rate would be proportional to body mass and the work of sliding as a fraction of the work of breathing would be smaller in larger animals.

Animals↗

PubMed2003

Life-long calorie restriction in Fischer 344 rats attenuates age-related loss in skeletal muscle-specific force and reduces extracellular space.

The decline in muscle function is associated with an age-related decrease in muscle mass and an age-related decline in strength. However, decreased strength is not solely due to decreased muscle mass. The age-related decline in muscle-specific force (force/muscle cross-sectional area), a measure of intrinsic muscle function, also contributes to age-related strength decline, and the mechanisms by which this occurs are only partially known. Moreover, changes in the extracellular space could have a profound effect on skeletal muscle function. Life-long calorie restriction in rodents has shown to be a powerful anti-aging intervention. In this study, we examine whether calorie restriction is able to attenuate the loss of muscle function and elevations in extracellular space associated with aging. We hypothesize that calorie restriction attenuates the age-associated decline in specific force and increases in extracellular space. Measurements of in vitro contractile properties of the extensor digitorum longus (type II) and soleus (type I) muscles from 12-mo and 26- to 28-mo-old ad libitum-fed, as well as 27- to 28-mo-old life-long calorie-restricted male Fischer 344 rats, were performed. We found that calorie restriction attenuated the age-associated decline in muscle mass-to-body mass ratio (mg/g) and strength-to-body mass ratio (N/kg) in the extensor digitorum longus muscle (P < 0.05) but not in the soleus muscle (P > 0.05). Importantly, muscle-specific force (N/cm2) in the extensor digitorum longus, but not in the soleus muscle, of the old calorie-restricted rats was equal to that of the young 12-mo-old animals. Moreover, the age-associated increase in extracellular space was reduced in the fast-twitch extensor digitorum longus muscle (P < 0.05) but not in the soleus muscle with calorie restriction. We also found a significant correlation between the extracellular space and the muscle-specific force in the extensor digitorum longus (r = -0.58; P < 0.05) but not in the soleus muscle (r = -0.38; P > 0.05). Hence, this study shows a loss of muscle function with age and suggests that long-term calorie restriction is an effective intervention against the loss of muscle function with age.

Aging↗

PubMed1997

Coding for auditory space in the nucleus of the brachium of the inferior colliculus in the ferret.

Coding for auditory space in the nucleus of the brachium of the inferior colliculus in the ferret. J. Neurophysiol. 78: 2717-2731, 1997. The nucleus of the brachium of the inferior colliculus (BIN) projects topographically to the deeper layers of the superior colliculus (SC), which contain a two-dimensional map of auditory space. In this study, we have used broadband stimuli presented in the free field to investigate how auditory space is represented in the BIN of the ferret. Response latencies and temporal firing patterns were comparable with those in the SC, and both properties showed some variation with stimulus location. We obtained spatial response profiles at two sound levels (5-15 and 25-35 dB above unit threshold). A large proportion of azimuth profiles (41% in the suprathreshold condition, 80% in the near-threshold condition) presented a single peak, indicating that they were tuned to single regions in space. For some of these units, the preferred speaker position varied considerably with sound level. The remaining units showed predominantly either broad "hemifield" or spatially ambiguous "bilobed" response profiles. At suprathreshold sound levels, the preferred azimuths of the tuned cells were ordered topographically along the rostrocaudal axis of the BIN, although this representation is considerably more scattered than that in the SC. In contrast to the SC, we observed no systematic variation in the distribution of near-threshold best azimuths, which were instead concentrated around the interaural axis in the contralateral hemifield. The azimuth tuning of individual units in the BIN was generally broader at both sound levels than that in the SC. Many units also were tuned for the elevation of the sound source (48% for supra-, 77% for near-threshold stimulation), but there was no evidence for topographic order in the distribution of preferred elevations within the BIN. These results suggest that the BIN sends inputs to the SC that are already selective for sound azimuth and elevation and that show some degree of topographic order for sound azimuth. These inputs then presumably are sharpened and their topography refined by a mechanism that is likely to involve convergence of other inputs and activity-dependent fine tuning of terminal connections, to result in a precise two-dimensional map of auditory space in the SC.

Acoustic Stimulation↗

PubMed2006

Recovering space in unilateral neglect: a neurological dissociation revealed by virtual reality.

Neglect patients often show deficits in responding to targets in the contra-lesional side of space. Past studies were able to ameliorate these deficits through manipulation of visual input. Here, the neural bases of the recovery of space following virtual reality (VR) training in neglect patients were investigated. Neglect patients were trained to respond to targets in the left side of space that appeared in the central or in the right side of space in a VR system. It was found that only patients with lesions that spared the inferior parietal/superior temporal regions were able to benefit from the VR training. It was concluded that these regions play a crucial role in the recovery of space that underlies the improvement of neglect patients when trained with VR. The implications of these results for determining the neural bases of a higher order attentional and/or spatial representation and for treating patients with unilateral neglect are discussed.

Aged↗

PubMed2002

New fiber formation in the interstitial spaces of rat skeletal muscle during postnatal growth.

The purpose of this study was to determine whether fiber hyperplasia occurs in the rat plantaris muscle during postnatal weeks 3-20. Total muscle fiber number, obtained via the nitric acid digestion method, increased by 28% during the early postnatal rapid growth phase (3-10 weeks), whereas the number of branched fibers was consistently low. Whole-muscle mitotic activity and amino acid uptake levels showed an inverse relationship to the increase in total fiber number. The expression of MyoD mRNA (RT-PCR) levels decreased from 3 to 20 weeks of age, as did the detection of anti-BrdU- and MyoD-positive cells in histological sections. Immunohistochemical staining patterns for MyoD, myogenin, or developmental myosin heavy chain on sections stained for laminin (identification of the basal lamina) and electron micrographs clearly indicate that de novo fiber formation occurred in the interstitial spaces. Myogenic cells in the interstitial spaces were negative for the reliable specific satellite cell marker M-cadherin. In contrast, CD34 (an established marker for hematopoietic stem cells)-positive cells were located only in the interstitial spaces, and their frequency and location were similar to those of MyoD- and/or myogenin-positive cells. These findings are consistent with fiber hyperplasia occurring in the interstitial spaces of the rat plantaris muscle during the rapid postnatal growth phase. Furthermore, these data suggest that the new fibers may be formed from myogenic cells in the interstitial spaces of skeletal muscle and may express CD34 that is distinct from satellite cells.

Amino Acids↗

PubMedDate not supplied

Use of a prospective space-time scan statistic to prioritize shigellosis case investigations in an urban jurisdiction.

OBJECTIVE: A prospective space-time scan statistic was applied to Chicago's 2002 shigellosis surveillance data to evaluate its utility in objectively describing clusters and assisting in the prioritization of investigations. METHODS: The prospective space-time module of SaTScan, a free software available online, was used to identify "live" clusters of disease, meaning cases that were current as of the date of the analysis and strongly associated in place and time. Fifty-two separate space-time analyses were run; one simulation for each week of 2002. Identified clusters were described in terms of space, time, risk factors reported by involved case-patients, and cases' links to venue-associated outbreaks. RESULTS: Twelve live clusters were detected at the p < 0.05 significance level: two single-household clusters and 10 community clusters. The community clusters ranged in size from 194 to 367 census tracts (median = 294), and in disease burden from 21 to 41 cases (median = 29). Geographically, all of the community clusters were located in the west-central part of the city and had a temporal span of 28 days. Within the 10 community clusters, 15 different day care centers were identified as potential exposure settings for case-patients or their close contacts. CONCLUSIONS: The prospective space-time scan statistic offers local health departments an objective way of describing clusters of shigellosis cases. The method used in this study could help prioritize the assignment and investigation of cases, particularly when overall shigellosis incidence exceeds expected numbers or when an agency's resources are stressed by other events, such as outbreaks.

Chicago↗

PubMed2003

Pure imagery hemi-neglect of far space.

Patients with hemispatial neglect restricted to near (within reaching distance) or to far space (beyond reaching distance) have been described. This constitutes a double-dissociation considered by current neurocognitive thinking as compelling evidence for separate networks. However, a similar double-dissociation exists with respect to perceived as opposed to imagined space. If the organization of represented space was similar to that of perceived space, it should contain a far/near dissociation as well. This paper describes a patient with pure representational neglect restricted to far space.

Aged↗

PubMed1989

The lumbar epidural space in patients examined with epiduroscopy.

Percutaneous epiduroscopy was performed in 10 patients with the aim of comparing the lumbar epidural space of the patients with the findings made earlier in autopsy subjects. The patients were scheduled for partial laminectomy for a herniated lumbar disc. A complete examination was possible in eight subjects. The extent of view was very limited. The epidural space opened up only temporarily as air was injected. The dura mater lay very close to the dorsal aspect of the epidural space and was attached to the flaval ligaments by a dorsomedian connective tissue band. The band was identified in all eight subjects and was found to cause a dorsal fold in the dura mater. An epidural catheter was introduced 2-5 cm into the space by midline puncture in four patients and by the paramedian approach in the other four. The catheter was visualized in two patients only when the paramedian approach was used. None of the midline catheters could be seen in the space. In 2 of the 10 subjects a moderate bleeding impaired the view and made complete examination impossible. Smaller bleeding occurred in three other subjects. The partial laminectomy performed one to two interspaces caudad to the level of endoscopy did not reveal any evidence of epidural bleeding in any subject. The postoperative course of all patients was uneventful.

Adult↗

PubMed2002

Effect of space flight on the frequency of micronuclei and expression of stress-responsive proteins in cultured mammalian cells.

Results of past space experiments suggest that the biological effect of space radiation could be enhanced under microgravity in some cases, especially in insects. To examine if such a synergistic effect of radiation and microgravity also exists in human cells, frequencies of chromosome instability and cellular levels of several stress-responsive proteins were analyzed in cultured human and rodent cells after space flight. Human (MCF7 and AT2KY), mouse (m5S) and hamster (SHE) cell lines were loaded on the Space Shuttle Discovery (STS-95 mission) and grown during a 9-day mission. After landing, the micronuclei resulting from abnormal nuclear division and accumulation of stress-responsive proteins such as p53 and mitogen-activated protein kinases (MAPKs), which are involved in radiation-induced signal transduction cascades, were analyzed. The frequencies of micronuclei in all the four mammalian cell strains tested were not significantly different between flight and ground control samples. Also, the cellular amounts of p53, p21 (WAF1/SDI1/CIP1) and activated (phosphorylated) forms of three distinct MAPKs in MCF7 and m5S cells of flight samples were similar to those of ground control samples. These results indicated that any effect of space radiation, microgravity, or combination of both were not detectable, at least under the present experimental conditions.

Animals↗

PubMed1983

Delay time correction of the gas analyzer in the calculation of anatomical dead space of the lung.

By means of a mathematical model, we have studied a way to correct the delay time of the gas analyzer in order to calculate the anatomical dead space using Fowler's graphical method. The mathematical model was constructed of ten tubes of equal diameter but unequal length, so that the amount of dead space varied from tube to tube; the tubes were emptied sequentially. The gas analyzer responds with a time lag from the input of the gas signal to the beginning of the response, followed by an exponential response output. The single breath expired volume-concentration relationship was examined with three types of expired flow patterns of which were constant, exponential and sinusoidal. The results indicate that the time correction by the lag time plus time constant of the exponential response of the gas analyzer gives an accurate estimation of anatomical dead space. Time correction less inclusive than this, e.g. lag time only or lag time plus 50% response time, gives an overestimation, and a correction larger than this results in underestimation. The magnitude of error is dependent on the flow pattern and flow rate. The time correction in this study is only for the calculation of dead space, as the corrected volume-concentration curves does not coincide with the true curve. Such correction of the output of the gas analyzer is extremely important when one needs to compare the dead spaces of different gas species at a rather faster flow rate.

Gases↗

PubMed2006

Free-end space maintainers: design, utilization and advantages.

Primary molars are a determining factor in the development of occlusion. Given their importance, when restorative treatment is notfeasible and a primary molar must be extracted, the practitioner should keep in mind the risk of losing space, and the consequent malocclusion. Preservation of the space can eliminate or reduce the needforprolonged orthodontic treatment. For that reason, there are various kinds of space maintainers and the pediatric dentist must decide which one to utilize, on the basis of general and local factors related to the child In the selection of a treatment option for space maintenance, the greatest complications occur when the first permanent molar has not yet erupted A large variety of appliances have been devised to deal with this situation. This article proposes the use of a removable space maintainer that is open on one end and can be employed to guide the first permanent molar, maintaining the integrity of the mucous membrane and serving as a prosthetic appliance, preventing the complications and contraindications often caused by sub-gingival maintainers.

Child↗

PubMed2006

Anaerobic digestion of space mission wastes.

The technical feasibility of applying leachbed high-solids anaerobic digestion for reduction and stabilization of the organic fraction of solid wastes generated during space missions was investigated. This process has the advantages of not requiring oxygen or high temperature and pressure while producing methane, carbon dioxide, nutrients, and compost as valuable products. Anaerobic biochemical methane potential assays run on several waste feedstocks expected during space missions resulted in ultimate methane yields ranging from 0.23 to 0.30 L g-1 VS added. Modifications for operation of a leachbed anaerobic digestion process in space environments were incorporated into a new design, which included; (1) flooded operation to force leachate through densified feedstock beds; and (2) separation of biogas from leachate in a gas collection reservoir. This mode of operation resulted in stable performance with 85% conversion of a typical space solid waste blend, and a methane yield of 0.3 Lg per g VS added after a retention time of 15 days. These results were reproduced in a full-scale prototype system. A detailed analysis of this process was conducted to design the system sized for a space mission with a six-person crew. Anaerobic digestion compared favorably with other technologies for solid waste stabilization.

Anaerobiosis↗