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At least 1,189 records · Page 66Linked to original sources
PubMed1992

Z-line/I-band and A-band lattices of intact frog sartorius muscle at altered interfilament spacing.

Muscle contraction has long been known to be affected by the osmolarity of the bathing solution. Part of this effect is caused by changes in interfilament spacing in the A-band. We have investigated the variation in spacing of the square lattice of thin filaments within and near the Z-line (the Z-line/I-band or Z-I lattice) in intact frog sartorius muscle over a wide range of osmolarities and compared it with the corresponding changes in the A-band lattice. Both lattices have a lower limit for compression and an upper limit for swelling. The spacing of the Z-I lattice is nearly proportional to that of the A-band, but shows a 2-3% variation at extreme shrinkage or swelling. In normal intact muscle, the osmotically-inactive volume of both lattices is between 20 and 30%. These in vivo measurements of lattice spacing differ significantly from those observed in electron micrographs. With moderate variations in osmolarity, lattice spacing and muscle fibre width show similar behaviour, but at extreme osmolarities, the lattice spacing changes less than the fibre width. An equatorial reflection was observed in intact muscle, previously identified in skinned muscle, which does not index on the A-band and which changes with osmolarity in a manner different from that observed for the A-band and Z-I lattices. This reflection may arise from changes in the ordering of the Z-I lattice or may involve components additional to the thick and thin filaments.

Actin Cytoskeleton↗
PubMed1988

Phase space electroencephalography (EEG): a new mode of intraoperative EEG analysis.

Intraoperative monitoring of electroencephalography (EEG) data can help assess brain integrity and/or depth of anesthesia. We demonstrate a computer generated technique which provides a visually robust display of EEG data plotted as 'phase space trajectories' and a mathematically derived parameter ('dimensionality') which may correlate with depth of anesthesia. Application of nonlinear mathematical analysis, used to describe complex dynamical systems, can characterize 'phase space' EEG patterns by identifying attractors (geometrical patterns in phase space corresponding to specific ordered EEG data subjects) and by quantifying the degree of order and chaos (calculation of dimensionality). Dimensionality calculations describe the degree of complexity in a signal and may generate a clinically useful univariate EEG descriptor of anesthetic depth. In this paper we describe and demonstrate phase space trajectories generated for sine waves, mixtures of sine waves, and white noise (random chaotic events). We also present EEG phase space trajectories and dimensionality calculations from a patient undergoing surgery and general anesthesia in 3 recognizable states: awake, anesthetized, and burst suppression. Phase space trajectories of the three states are visually distinguishable, and dimensionality calculations indicate that EEG progresses from 'chaos' (awake) to progressively more 'ordered' attractors (anesthetized and burst suppression).

Electroencephalography↗
PubMed1988

Length and myofilament spacing-dependent changes in calcium sensitivity of skeletal fibres: effects of pH and ionic strength.

The calcium sensitivity of force was measured in glycerinated rabbit psoas fibres at sarcomere lengths (SL) from 2.3 to 3.4 micron. Increased SL caused calcium sensitivity to increase and the slope of force-calcium relations to decrease. We have hypothesized that length-dependent changes in myofilament lattice spacing and the presence of fixed charge on the myofilaments are important in determining calcium sensitivity. Lattice spacing changes were monitored by measuring fibre diameter (D). D was decreased by increasing SL, decreasing bathing solution pH and by osmotic compression with 3% PVP. 3% PVP caused D to decrease by about 15% at all SLs and pH values tested. Force-calcium relations were measured at different SLs and pH values, with and without 3% PVP in the bathing solutions. At all pH values D at SL 2.3 micron with 3% PVP was comparable to the value at 3.4 micron, without PVP. At pH 7.5 and 7.0 calcium sensitivity was about the same at both SL, although the slope of the force-calcium relation was less at longer SL. The similarity of the calcium sensitivity at the same D, but much different SL, indicates that lattice spacing is important in determining calcium sensitivity, while SL and the degree of myofilament overlap are important in determining the slope of force-calcium relations. In order to test for the role of myofilament charge in determining calcium sensitivity, pH and ionic strength were varied. Decreasing pH caused decreased maximum force and calcium sensitivity. In addition, the influence of SL on calcium sensitivity decreased as pH was lowered, with minimal SL dependence at pH 5.5; even though lattice spacing still decreased with increasing SL. When D was decreased with PVP, calcium sensitivity increased at all SLs in pH 7.5 and 7.0 while the same lattice spacing changes at pH 6.0 and 5.5 resulted in greatly reduced shifts in calcium sensitivity. These results indicate that the effect of lattice spacing on calcium sensitivity depends on myofilament charge. At pH 6.0, even though osmotic compression of the lattice has no effect, increasing SL causes about half the shift in calcium sensitivity seen at pH 7.0. Lowering ionic strength from 200 to 110 mM caused an increase in both the magnitude and length dependence of calcium sensitivity at pH 7.0, while at pH 5.5 both decreased.(ABSTRACT TRUNCATED AT 400 WORDS)

Actin Cytoskeleton↗
PubMed1990

A comparative study of the spaces between the metacarpal and metatarsal heads.

The study of the spaces between the metacarpal heads on 23 cadavers, raises the question of the existence of bursae at this level. This is in line with recent studies suggesting that such bursae are present at this level in the foot. Careful dissection and histological studies revealed characteristics compatible with both of the following hypotheses: either the existence of bursae not described until now in anatomy text-books, or spaces limited by a cul-de-sac of the aponeuroses of the hand in the 2nd, 3rd and 4th digits. Tissue analyses that could determine more specifically the nature of the limiting membrane of these spaces, as well as pathological studies demonstrating the occurrence of common anomalies of bursae in these spaces, are required in order to conclude definitively the nature of the spaces between the metacarpal heads. The gross anatomical and histological characteristics of the spaces between the metacarpal and metatarsal heads and of their limiting membranes were compared and found to be analogous in our series.

Humans↗
PubMed1998

Column spacing in normal and visually deprived monkeys.

A recent model for the development of the pattern of eye-dominance domains in primary visual cortex predicts that stimulus conditions during early visual life determine the spacing (or periodicity) of ocular dominance columns (ODC). The model predicts that normal binocular visual experience consists of highly correlated binocular stimulation and leads to relatively narrow ODC spacing, while abnormal binocular visual stimulation attendant with strabismus consists of non-correlated, incoherent, and asynchronous stimulation and leads to wider than normal ODC spacing. Evidence in support of the model has been presented for strabismus in the kitten. We tested the predictions of the model in normal monkeys and others subjected to various forms of abnormal visual experience during infancy. We identified and measured the inter-column spacing (or periodicity) in the V1 cortex of 19 adult monkeys (M. mulatta) using the cytochrome-oxidase (CO) histochemical method. There were no significant differences in the V1 inter-column spacing between normal adult monkeys (n=5) and other adult monkeys having had monocular-form deprivation (n=5), experimental anisometropia (n=5), or experimental strabismus (n=4) early in life. The quality of early binocular visual experience is not a significant determinant of the inter-column spacing in primate V1 cortex. Therefore, the model predicting an increase in the ODC periodicity with strabismus is not supported.

Analysis of Variance↗
PubMed2001

Bisphosphonate space measurement and dosage requirement for intravenous clodronate treatment of Paget's disease.

It has been claimed that the bisphosphonate space, a scintigraphic technique which simultaneously estimates bone uptake and renal clearance of bisphosphonate, can be used to predict the dose of bisphosphonate required to induce biochemical remission in Paget's disease. In a prospective study of 15 newly diagnosed patients with Paget's disease, bisphosphonate space measurements were made prior to treatment with intravenous clodronate. Treatment with clodronate 0.6 g was given four times weekly until the alkaline phosphatase (ALP) suppressed below the upper level of the reference range (120 u/l) or reached a plateau, and the cumulative dose required (1.8-7.8 g) was calculated. Overall, the bisphosphonate space correlated poorly with the total dose requirement (r = 0.441, P = 0.100), but the relationship was weakened by an outlier, who had the poorest renal function. Excluding this subject improved the correlation coefficient (r = 0.852, P <0.0001). The relationship between dose requirement and log10 initial ALP was not as strong (r = 0.672, P <0.01). However, for both ALP and the bisphosphonate space the 95% prediction intervals were wide. We conclude that the bisphosphonate space does relate to dose requirements for intravenous bisphosphonates, but that it is unreliable when renal function is poor, and may not offer much gain over the pretreatment ALP levels. Both ALP and the bisphosphonate space have wide prediction intervals, and are therefore poor guides to dose requirement.

Aged↗
PubMed1998

Dilated Virchow-Robin spaces: MRI pathological study.

We performed a histopathological study of two human brains to look at dilated Virchow-Robin (V-R) spaces in the anterior perforated substance and putamen. We measured the diameter of 74 arteries in 54 dilated V-R spaces. In 28 patients without neurological deficits we ascertained the characteristic location of dilated V-R spaces in the anterior perforated substance and basal ganglia on MRI, measuring the distance from 64 foci of cerebrospinal fluid signal intensity to the centre of the mamillary body on 1 mm thick images. In the histopathological study, the mean diameter of the arteries was 39.0 +/- 36.0 microns. Dilatation of the V-R space was observed from the end of the indentation of the pial membrane towards the brain surface along the perforating artery. In the MR images, the mean distance from the dilated V-R space to the mamillary body was 10.0 +/- 4.5 mm. The V-R space was confined to a fixed level in the lower part of the basal ganglia, and not found near the brain surface.

Adult↗
PubMed2005

Spontaneous development of bilateral subdural hematomas in an infant with benign infantile hydrocephalus: color Doppler assessment of vessels traversing extra-axial spaces.

We present an infant with macrocrania, who initially demonstrated prominent extra-axial fluid collections on sonography of the brain, compatible with benign infantile hydrocephalus (BIH). Because of increasing macrocrania, a follow-up sonogram of the brain was performed; it revealed progressive enlargement of the extra-axial spaces, which now had echogenic debris. Color Doppler US showed bridging veins traversing these extra-axial spaces, so it was initially thought that these spaces were subarachnoid in nature (positive cortical vein sign). However, an arachnoid membrane was identified superior to the cortex, and there was compression of true cortical vessels beneath this dural membrane. An MRI of the brain showed the extra-axial spaces to represent bilateral subdural hematomas. The pathogenesis of spontaneous development of the subdural hematomas, in the setting of BIH, is discussed. We also emphasize that visualizing traversing bridging veins through extra-axial spaces does not necessarily imply that these spaces are subarachnoid in origin.

Brain↗
PubMed1998

Distinguishing silent lacunar infarction from enlarged Virchow-Robin spaces: a magnetic resonance imaging and pathological study.

We studied clinicopathological correlations between magnetic resonance imaging (MRI) appearances of postmortem brains and pathological findings in 12 patients to identify simple criteria with which to distinguish lacunar infarctions from enlarged Virchow-Robin spaces. In vivo MRI was also available for 6 of the 12 patients. We focused on small, silent, focal lesions including lacunar infarctions and enlarged Virchow-Robin spaces that were confirmed pathologically. From a total of 114 lesions, enlarged Virchow-Robin spaces were most often found in the basal ganglia and had a round or linear shape. Lacunar infarctions also were most frequent in the basal ganglia, but 47% of these were wedge-shaped. In the pathological studies, excluding lesions from the lower basal ganglia region, enlarged Virchow-Robin spaces were usually smaller than 2 x 1 mm. The shapes and sizes of the lesions determined by MRI (in vivo and postmortem) concurred with the pathological findings, except that on MRI the lesions appeared to be about 1 mm larger than found in the pathological study. When lesions from the lower basal ganglia and the brain stem regions are excluded, the sensitivity and specificity for discriminating enlarged Virchow-Robin spaces from lacunar infarctions are optimal when their size is 2 x 1 mm or less in the pathological study (79%/75%, respectively), 2 x 2 mm or less in both of the MRI studies: postmortem (81%/90%), and in vivo (86%/91%). In conclusion, we were able to differentiate most lacunar infarctions from enlarged Virchow-Robin spaces on MRI on the basis of their location, shape and size. We stress that size is the most important factor used to discriminate these lesions on MRI.

Aged↗
PubMed2006

On the elusiveness of enemy-free space: spatial, temporal, and host-plant-related variation in parasitoid attack rates on three gallmakers of goldenrods.

Host shifting by phytophagous insects may play an important role in generating insect diversity by initiating host-race formation and speciation. Models of the host shifting process often invoke reduced rates of natural enemy attack on a novel host in order to balance the maladaptation expected following the shift. Such "enemy-free space" has been documented for some insects, at some times and places, but few studies have assessed the occurrence of enemy-free space across years, among sites, or among insect species. We measured parasitoid attack rates on three insect herbivores of two goldenrods (Solidago altissima L. and Solidago gigantea Ait.), with data from multiple sites and multiple years for each herbivore. For each insect herbivore, there were times and sites at which parasitoid attack rates differed strongly and significantly between host plants (that is, enemy-free space existed on one host plant or the other). However, the extent and even the direction of the attack-rate difference varied strongly among sites and even among years at the same site. There was no evidence of consistent enemy-free space for any herbivore on either host plant. Our data suggest that enemy-free space, like many ecological and evolutionary forces, is likely to operate as a geographic and temporal mosaic, and that conceptual models of host shifting that include enemy-free space as a consequence of host novelty are likely too simple.

Animals↗
PubMed1989

A new technique of identifying the epidural space "dripping infusion method".

We developed a new visual technique o identifying the epidural space, using the hydrostatic pressure produced by a suspended micro-drip intravenous apparatus. When the needle pierces the ligamentum flavum, the resistance to positive pressure disappears and the saline in the apparatus flows freely into the epidural space. Thus, the entry of the needle point into the epidural space is visually confirmed by the appearance of dripping flow in the drip bulb (dripping infusion sign). This procedure was clinically evaluated at the thoraco-cervical area in 114 patients; the thoracic area in 116; and the lumbar area in 272, respectively. In 491 (97.8%) of the patients, the epidural space was identified with facility. In the remaining 11 patients (2.2%), a false dripping infusion sign appeared at the more superficial site than expected. If the pressure waveform in the epidural space is analyzed, the correct positioning of the needle can be easily confirmed. We believe that this method is one of the most accurate visual methods of identifying the epidural space and useful for teaching the epidural blockade to students and residents.

Journal Article↗
PubMed1983

Prevalence and correlates of posterior extra echocardiographic spaces in a free-living population based sample (the Framingham study).

To obtain epidemiologic information on extra echocardiographic spaces immediately posterior to the left ventricular free wall, 2,028 subjects in the original Framingham cohort study (mean age 70 +/- 7 years) and 3,624 of the offspring of the cohort (and their spouses) (mean age 44 +/- 10 years) with adequate echocardiograms were evaluated. Extra echocardiographic spaces were detected in 370 (6.5%) of the 5,652 subjects. The prevalence ranged from less than 1% in subjects in the 20- to 30-year age decade to greater than 15% for those in their 80s. Extra echocardiographic spaces tended to be more common in subjects who were older, female, obese, more hypertensive, and who had higher blood sugar levels and higher low density lipoprotein cholesterol levels (measured 8 years earlier). The high prevalence of extra echocardiographic spaces and the independent association with age (cohort and offspring), obesity (cohort and male offspring), and ventricular septal hypertrophy (cohort and male offspring) is compatible with at least 2 hypotheses among others that should be tested: (1) Subepicardial fat may often masquerade as pericardial fluid producing a posterior extra echocardiographic space, especially in obese elderly subjects. (2) Small posterior extra echocardiographic spaces may often be early markers of subclinical hypertensive heart disease.

Adolescent↗
PubMed1977

Space utilization of Peromyscus: social and spatial factors.

Space utilization of Peromyscus maniculatus bairdi and P. leucopus noveboracensis was studied in laboratory enclosures. After 1 week, individuals were given access to twice as much space for an additional week. The new rea was either vacant or was occupied by a similarly experienced conspecific of the same or opposite sex. Patterns of space utilization and reaction to the doubling of space were species specific. Each species displayed specific patterns of social behaviour and only P. maniculatus reproduced. Both species exhibited similar patterns of space utilization in the presence of another individual. Social regulation of space utilization did not result from territorial defence of mutually exclusive areas, but from the initial mutual avoidance of two individuals.

Aggression↗
PubMed1990

Thoracoplasty: current application to the infected pleural space.

Thoracoplasty, once commonly used in the management of cavitary pulmonary disease, continues to find application in the obliteration of infected pleural spaces. This study reports a series of 13 patients receiving thoracoplasty between 1976 and 1989. Five patients had chronic apical empyema spaces without prior resection of lung tissue. Two of the empyemas were due to tuberculosis, two were due to atypical mycobacteria, and one was due to postpneumonic empyema. All patients had extensive destruction of upper lobe tissue. Eight patients had undergone prior pulmonary resection; 3 had persistent infected spaces in the early postoperative period, 3 had development of empyemas and bronchopleural fistulas late (5 to 19 years) after pulmonary resection, and 2 had postpneumonectomy empyema. All patients had rigid cavity walls preventing space obliteration by rib removal alone and required concomitant resection of the thickened pleura and intercostal muscle tissues. Bronchopleural fistulas were present in 11 patients and were closed with adjacent nonintercostal muscle. All patients survived and had successful obliteration of the infected spaces with acceptable physiological and cosmetic results. We conclude that thoracoplasty remains a useful procedure in the management of the infected pleural space in select patients.

Adult↗
PubMed1989

A method for determining optimal interelectrode spacing for cerebral topographic mapping.

Inappropriately large interelectrode spacing may result in significant errors of localization and erroneous measurements of amplitudes, due to aliasing. Oversampling with very large numbers of scalp electrodes is impractical. We present a generally applicable method for determination of optimal interelectrode spacing. This optimal spacing is computed from the Nyquist distance for the potential of interest. For most potentials, the bandwidth of the topographic distribution is not known, so it must be first measured by oversampling with tightly spaced electrode arrays. The Nyquist distance will vary for different types of cerebral potentials, different components of a given potential, and for different areas of the scalp. We have determined the Nyquist distances for interelectrode spacing necessary to record accurately the geographically small components of the SEP in the region of the sensory strip. These distances are less than 3 cm, which is significantly smaller than the 7 cm distance of the 10-20 system. Recordings of SEPs in this region made with larger spacings may have significant errors. Recordings made at the Nyquist distance may be precisely interpolated to arbitrary accuracy.

Brain Mapping↗
PubMedDate not supplied

Calculating the probability that microcracks initiate resorption spaces.

This paper explores the assumptions and limitations of the probability calculation that led to the conclusion by Burr et al. (1985) that microcracks initiate new remodeling events. It also corrects several minor errors in the calculation in the original manuscript. The results show that the probability that cracks and resorption spaces are associated depends heavily on a factor, F, that accounts for the possibility that some osteons that contain both a crack and a resorption space share a cement line with an adjacent osteon to which the crack more properly 'belongs.' F in turn depends on (1) the measurement criteria for cracks and resorption spaces, (2) the osteon population density in the bone, and (3) the mechanism by which cracks initiate remodeling. The theoretical maximum number of osteons that can contain both a crack and a resorption space (nmax) increases as the number of resorption spaces (r), the number of cracks (c), and F increase, but decreases as the osteon population density (d) increases. A larger nmax makes a direct association between cracks and resorption spaces more difficult to demonstrate experimentally.

Animals↗
PubMed1984

Changes in the lateral filament spacing of skinned muscle fibres when cross-bridges attach.

When a skinned fibre prepared from frog skeletal muscle goes from the relaxed to the rigor state at a sarcomere length of about 2.2 micron, the 1, 0 transverse spacing of the filament lattice, measured by X-ray diffraction, decreases by about 11%. In measurements at various sarcomere lengths, the decrease in the spacing was approximately proportional to the degree of overlap between the thick and thin filaments. This suggests that the shrinkage of the lattice is caused by a lateral force produced by cross-bridges. In order to estimate the magnitude of the lateral force, the decrease of spacing between relaxed and rigor states was compared with the shrinkage caused osmotically by adding a high molecular weight polymer, polyvinylpyrrolidone, to the bathing solution. The results indicate that the lateral force produced per unit length of thick filament in the overlap zone is of the same order of magnitude as the axially directed force produced during maximum isometric contraction (10(-10) to 10(-9) N/micron). Experiments in the presence of a high concentration of polyvinylpyrrolidone (100 g/l) show that when the lattice spacing is decreased osmotically beyond a certain value, the lateral force produced when the fibre goes into rigor changes its direction, causing the lattice to swell. This result can be explained by assuming that there is an optimum interfilament spacing at which the cross-bridges produce no lateral force. At other spacings, the lateral force tends to displace the filament lattice toward that optimum value.

Animals↗
PubMed2004

[Na(+)] in the subsarcolemmal 'fuzzy' space and modulation of [Ca(2+)](i) and contraction in cardiac myocytes.

The strength of the heart beat depends on the amplitude and time course of the transient increase in [Ca(2+)] in the myocytes with each cycle. [Na(+)](i) modulates cardiac contraction through its effect on the Ca(2+) flux through the Na/Ca exchanger. Cardiac excitation-contraction coupling has been postulated to occur in a microdomain or 'fuzzy' space at the junction of the T-tubules and the sarcoplasmic reticulum. This 'fuzzy' space is well described for the Ca(2+) fluxes and the interaction between the L-type Ca(2+) channel, the Ca(2+) release channel of the sarcoplasmic reticulum and the Na/Ca exchanger. Co-localization of the Na(+) transporters, in particular the Na/K pump and the Na(+) channel, within this 'fuzzy' space is not as well established. The functional and morphological characteristics of the 'fuzzy' space for Na(+) and its interaction with the Ca(2+) handling suggest that this space is not strictly co-inciding with the Ca(2+) microdomain. In this space [Na(+)] can be several-fold higher or lower than [Na(+)] in the bulk cytosol. This has implications for modulation of [Ca(2+)](i) during a single beat as well as during alterations in Na(+) fluxes seen in pathological conditions.

Animals↗