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At least 1,603 records · Page 89Linked to original sources
PubMed1987

Mechanics of the pleural space: fundamental concepts.

The transmission of forces from the respiratory muscles to the lung across the extremely thin pleural space has been poorly understood because of the difficulty of accurately measuring pleural liquid and pleural surface pressure (lung static recoil or transpulmonary pressure). Recent results using relatively noninvasive techniques have indicated that the vertical gradient in pleural liquid pressure is not hydrostatic, that pleural liquid pressure is closely related to lung recoil, and that there exists a very thin but continuous pleural liquid layer. These findings contradict concepts based on hydrostatic equilibrium and on the distinction between pleural liquid and pleural surface pressure due to pleural contact. Pleural liquid pressure is not in hydrostatic equilibrium because the difference between the vertical gradient in pleural liquid pressure and the effect of gravity is always balanced by a pressure loss due to a viscous flow within the pleural space. Fluid lubrication of the pleural surfaces is the primary function of the pleural space. The mechanical interaction between the lung and the chest wall is coupled to the dynamics of liquid within the pleural space, which is viewed as a flow-through system. Homeostasis is achieved in such a system by the adjustment of the viscous flow within the pleural space and the outflow absorption rate by lymphatics to the microvascular filtration rate across pleural capillaries.

Animals↗
PubMed2002

A new technique for muscle flap closure of the empyema space in complicated chronic bronchopleural fistula. Wedging the causative bronchus with a plug.

OBJECTIVES: It is difficult to close the empyema space once it is opened, especially in cases complicated with a chronic bronchopleural fistula. A muscle flap closure is generally employed to prevent this situation. However, this operation occasionally fails because the space newly recurs around the fistula due to atrophic change occurring in these translocated muscles. The aim of the present new technique was to prevent inspiratory pressure from the inside of the bronchus by bronchial emboli, and help the adhesion between the fistula stump and the muscle flap, even if they have become atrophic and no longer have sufficient volume to fill the entire empyema space. METHODS: We carried out fiberscopic embolism of causative bronchioles followed by muscle flap closure in 4 patients in whom open drainage had already been performed against parapneumonic empyema within the bronchial fistula. The bronchial fistula was plugged from the inside of the bronchus by silicon material, and stainless steel wire was used to connect this plug tightly to the muscle flaps, so that the fistula was sandwiched between them. In all cases, we succeeded in complete closure of the bronchial fistula and empyema space without using the omentum, and there has been no recurrence. CONCLUSION: The presented new technique was beneficial for achieving muscle flap closure of the empyema space with a chronic bronchopleural fistula.

Bronchi↗
PubMed2006

Space-time clustering analyses of type 1 diabetes among 0- to 29-year-olds in Yorkshire, UK.

AIMS/HYPOTHESIS: Infections have been suggested to play a role in the aetiology of type 1 diabetes. The presence of space-time clustering is consistent with the notion of an environmental component in disease aetiology, possibly linked to infections. We tested for evidence of space-time clustering among children and young adults under 30 years of age using data from a population-based register in Yorkshire, UK. SUBJECTS AND METHODS: Two data sets of children and young people diagnosed with type 1 diabetes were analysed: (1) children aged 0-14 years and resident in Yorkshire during 1978-2002; (2) those aged 15-29 years and resident in West Yorkshire during 1991-2002. Tests for space-time interactions between cases were applied. Addresses at diagnosis were geo-coded and used as the basis for the analyses. RESULTS: The study analysed 3,019 type 1 diabetic patients in the 0-14 years age group and 989 patients in the 15-29 years group. Statistically significant space-time clustering based on place and time of diagnosis was detected both for the 10-14-year-olds (p=0.04) and for the 15-19-year-olds (p=0.01). CONCLUSIONS/INTERPRETATION: Previous studies of clustering of type 1 diabetes have generally been restricted to childhood. Our results from a data set that includes teenagers and young adults show that space-time clustering was limited to young people aged 10-19 years. This finding is consistent with an aetiology involving late exposure to infection. However, the question of whether this is directly diabetogenic or unmasks latent diabetes cannot be addressed by this methodology.

Adolescent↗
PubMed2002

Two-dimensional analysis of the spacing of ocular dominance columns in normally raised and strabismic kittens.

In the primary visual cortex of cats, ferrets and macaque monkeys, the thalamocortical afferents conveying signals from the two eyes terminate in alternating regions of layer IV known as ocular dominance columns. Previous experiments have indicated that the periodicity of these columns can be influenced by visual experience: compared to normally raised animals both strabismic cats and cats raised with alternating monocular exposure displayed an increased spacing of adjacent ocular dominance columns in the primary visual cortex (area 17). However, recently it was shown that the formation of ocular dominance columns begins much earlier than previously supposed, indicating that early visual experience might only have a limited influence on the development of the spatial pattern of ocular dominance columns. We therefore visualized the complete pattern of ocular dominance columns in area 17 of normally raised and strabismic kittens during early postnatal development (age 3-6 weeks), particularly focussing on littermates. In addition, we used a previously developed spatial analysis (period statistics) to quantify columnar spacing two-dimensionally. We observed a pronounced interindividual variability in both normally raised and strabismic animals, with column spacings ranging from 783 to 1362 microm. In contrast to previous reports, there were no significant differences in columnar periodicity between normally raised and strabismic cats. These data indicate that rearing has less influence on column spacing while the interindividual variability is much greater than previously supposed, suggesting that genetic differences have an influence on column spacing.

Animals↗
PubMed2006

Creating defensible space in the wildland-urban interface: the influence of values on perceptions and behavior.

We examined the effect that value orientation to forests and wildland fire management has on an individual's decision to create defensible space around his or her residence in the wildland-urban interface. Using data from a mail-back questionnaire, respondents in north central Minnesota were clustered by basic value-laden beliefs toward forest and wildland fire management and compared across a number of perceptions and behaviors related to creating defensible space around residences. Value orientation groups differed in attitudes, subjective norms, and perceived behavior control toward creating defensible space. In addition, relative effects of these perceptions on intention to create defensible space differed across groups. Implications lie in (a) understanding differences in motivations and reasons for support of strategies for managing fires near the wildland-urban interface, (b) developing information designed to address the perspectives of different groups related to creating defensible space, and (c) contributing to an improved integration of land management and public concerns and interests.

Attitude↗
PubMed1999

K-space sampling strategies.

The k-space algorithm offers a comprehensive way for classification and understanding of the imaging properties of all commonly used MR sequences. This presentation describes the basic concepts of k-space and its most relevant properties for MR imaging. The ramifications of k-space sampling is discussed for the most commonly used groups of MR sequences including gradient-echo techniques, echo-planar imaging, spin echo, and rapid acquisition relation enhanced imaging (e. g., turbo spin echo, fast spin echo). In addition, the basic problems and properties of sequences based on non-rectilinear k-space sampling, such as spiral imaging, are discussed. Their artifact behavior is significantly different from rectilinear scans, which project all imperfections along the phase-encoding directions, whereas the artifact produced by spirals are more complex and not always easily recognizable as such. An understanding of the k-space sampling offers important insight into the basic properties of a given sequence regarding signal-to-noise ratio, image distortion, resolution and contrast. It is demonstrated that the ultimate limitation in imaging speed is given by the loss of signal-to-noise ratio inherent to faster data sampling.

Algorithms↗
PubMed2002

Stimulation of elongation growth and xyloglucan breakdown in Arabidopsis hypocotyls under microgravity conditions in space.

Seedlings of Arabidopsis thaliana (L.) Heynh. (ecotype Columbia and an ethylene-resistant mutant etr1-1) were cultivated for 68.5, 91.5 and 136 h on board during the Space Shuttle STS-95 mission, and changes in the elongation growth and the cell wall properties of hypocotyls were analyzed. Elongation growth of dark-grown hypocotyls of both Columbia and etr1-1 was stimulated under microgravity conditions in space. There were no clear differences in the degree of growth stimulation between Columbia and etr1-1, indicating that the ethylene level was not abnormally high in the cultural environment of this space experiment. Microgravity also increased the mechanical extensibility of cell walls in both cultivars, and such an increase was attributed to the increase in the apparent irreversible extensibility. The levels of cell wall polysaccharides per unit length of hypocotyls decreased in space. Microgravity also reduced the weight-average molecular mass of xyloglucans in the hemicellulose-II fraction. Also, the activity of xyloglucan-degrading enzymes extracted from hypocotyl cell walls increased under microgravity conditions. These results suggest that microgravity reduces the molecular mass of xyloglucans by increasing xyloglucan-degrading activity. Modifications of xyloglucan metabolism as well as the thickness of cell wall polysaccharides seem to be involved in an increase in the cell wall extensibility, leading to growth stimulation of Arabidopsis hypocotyls in space.

Adaptation, Physiological↗
PubMed2001

Incidence of deep fascial space infection after surgical removal of the mandibular third molars.

Nine hundred and ninety-three patients who underwent surgical removal of the mandibular third molars with oral antibiotic prophylaxis were examined to determine the incidence of postoperative deep fascial space infection and its background factors. Postoperative deep fascial space infection was observed in 8 of the patients (0.8%; 4 males and 4 females), and submandibular spaces were involved in all infected patients. Only 1 of these 8 patients was an immune compromised host. Patients aged 30 years or more had a significantly higher incidence of deep fascial space infection than those aged under 30. Five patients had partial bony impactions and 3 had complete bony impactions. However, the incidence of infection according to the molar positions was not significantly different between partial bony impaction and complete bony impaction. The 8 patients had not had pericoronitis preoperatively. The clinical courses of all were favorable after antibiotics were administered intravenously. In conclusion, the incidence of deep fascial space infection after removal of the mandibular third molars was low, at 0.8%. However, it may be desirable to remove the molars, if applicable, at a younger age because of the higher incidence of infection in patients aged over 30. The results of this study also offer information that will be useful as a basis for obtaining informed consent from patients whose mandibular third molars are to be removed.

Adolescent↗
PubMed2004

The body schema and the multisensory representation(s) of peripersonal space.

In order to guide the movement of the body through space, the brain must constantly monitor the position and movement of the body in relation to nearby objects. The effective 'piloting' of the body to avoid or manipulate objects in pursuit of behavioural goals (Popper & Eccles, 1977, p. 129), requires an integrated neural representation of the body (the 'body schema') and of the space around the body ('peripersonal space'). In the review that follows, we describe and evaluate recent results from neurophysiology, neuropsychology, and psychophysics in both human and non-human primates that support the existence of an integrated representation of visual, somatosensory, and auditory peripersonal space. Such a representation involves primarily visual, somatosensory, and proprioceptive modalities, operates in body part-centred reference frames, and demonstrates significant plasticity. Recent research shows that the use of tools, the viewing of one's body or body parts in mirrors, and in video-monitors, may also modulate the visuotactile representation of peripersonal space.

Journal Article↗
PubMed1984

Transesophageal atrial pacing threshold: role of interelectrode spacing, pulse width and catheter insertion depth.

This study evaluated the role of interelectrode spacing, pulse widths greater than 10 ms, and depth of esophageal insertion on minimizing transesophageal atrial pacing threshold in 30 patients aged 1 day to 77 years. Interelectrode spacings of 15, 22 and 28 mm were evaluated by establishing strength-duration curves in 2 or more serial studies in 12 patients; electrode spacing had no effect on pacing threshold. In 23 patients studied with 22-mm electrode spacing, pulse widths of 15 and 20 ms had no significant effect on current threshold requirements compared with 10-ms pulse widths. In 20 patients, pacing threshold and esophageal electrograms were obtained at 1.0- to 2.5-cm intervals with a 22-mm lead using a pulse width of 10 ms. Average minimal pacing threshold was 10.2 mA (range 4.5 to 20). The site of minimal pacing threshold was highly correlated with patient height (r = 0.987), and occurred within 1.1 cm (0 to 2.5 cm) of the site of the maximal bipolar atrial electrogram amplitude and 0.95 cm (0 to 3 cm) of the site of the maximal unipolar atrial electrogram. Bipolar electrode spacing of 15, 22 or 28 mm has little effect on transesophageal pacing threshold. In most patients, pulse widths greater than 10 ms do not significantly decrease pacing threshold. Correct catheter insertion depth is critical to minimize pacing threshold and may be predicted by either the site of the maximal atrial electrogram amplitude or patient height.

Adolescent↗
PubMed1981

Reliability and validity of lower third molar space-assessment techniques.

Present techniques for predicting eruption or impaction of lower third molars are based on measurements of the space between the second molar and the ramus. This study was designed to investigate the reliability and validity of radiographic techniques often used for assessing this space. Rotational tomograms (O.P.G.s) yielded the best estimates of the Space Width Ratio (found by dividing the space available by the mesiodistal width of the lower third molar) as measured directly on dried skulls. Estimates for lateral cephalograms were unreliable. The use of Xi point to lower second molar for assessing the space for lower third molars is not supported.

Adult↗
PubMed1987

Dynamic compartmentation of adenine nucleotides in the mitochondrial intermembrane space of rat-heart mitochondria.

To investigate whether or not the mitochondrial intermembrane space together with the extramitochondrial space form a homogeneous pool for adenine nucleotides, rat-heart mitochondria were studied in reconstituted systems with pyruvate kinase and ADP-producing enzymes with varied localization. In the hexokinase system, ADP is produced extramitochondrially by added yeast hexokinase, whereas in the creatine kinase system mitochondrial creatine kinase is responsible for ADP regeneration in the intermembrane space. The dependence of mitochondrial respiration on the extramitochondrial [ATP]/[ADP] ratio in both systems was investigated experimentally and by means of computer simulation. Near the resting state, higher [ATP]/[ADP] ratios were found in the creatine kinase system than in the hexokinase system at the same rate of respiration. This and the maintaining of a substantial creatine kinase-stimulated respiration in the presence of pyruvate kinase in excess is explained by a two-compartment model considering diffusion limitations of adenine nucleotides. A diffusion rate constant of (8.7 +/- 4.7) 10(4) microliters X mg-1 X min-1 for ADP and ATP was estimated, resulting in rate-dependent concentration differences up to 13.7 microM AdN between the extramitochondrial space and the AdN-translocator at the maximum rate of oxidative phosphorylation of rat-heart mitochondria. The results support the assumption that ADP diffusion towards the AdN-translocator is limited if its extramitochondrial concentration is low, resulting in a dynamic compartmentation of adenine nucleotides in the mitochondrial intermembrane space.

Adenine Nucleotides↗
PubMed1981

The spaces between membrane bilayers within PNS myelin as characterized by X-ray diffraction.

X-ray diffraction data from a wide range of animals characterize the two spaces in the peripheral nervous system (PNS) and the central nervous system (CNS) myelins. The 'extracellular space' is nearly constant from species to species while the 'cytoplasmic space' is more variable. A profile of swollen rat sciatic myelin shows material projecting from the bilayer into the extracellular space. Interdigitating Po molecules therefore are proposed to separate neighboring myelin bilayers across the extracellular space in PNS.

Animals↗
PubMed1985

Kinetics of macromolecules injected into the subretinal space.

Small, experimental, non-rhegmatogenous retinal detachments (blebs) in rabbit eyes resorbed 50% more slowly when filled with autologous serum than with Hanks' solution. To study the fate of large molecules in the subretinal space, carboxyfluorescein and several sizes of FITC-dextrans were injected into blebs and their movement followed by fluorophotometry. Carboxyfluorescein diffused quickly into the vitreous and was gone from the space after 8 hr. FITC-dextran 10-S (smaller than albumin) also diffused readily into the vitreous and took about 30 hr to be eliminated from the subretinal space. The diffusion of FITC-dextran 70-S and 150-S (both larger than albumin) was markedly slower, and roughly 80% of the 150-S was still present in the subretinal space after 3 days. Since the subretinal fluid in all of these blebs resorbed within 10 hr, the physiologic mechanisms for fluid resorption and elimination of large substances appear to be independent. Damaging the RPE barrier with sodium iodate allowed even the larger FITC-dextrans to exit from the subretinal space.

Absorption↗
PubMed1992

The role of adenylate kinase in dynamic compartmentation of adenine nucleotides in the mitochondrial intermembrane space.

To investigate the existence of dynamic adenine nucleotide (AdN) compartment in the mitochondrial intermembrane space, we used reconstituted systems consisting of (i) functional intact liver and heart mitochondria and (ii) pyruvate kinase plus phosphoenolpyruvate, both competing for ADP either formed in the intermembrane space by adenylate kinase or added directly into, or regenerated by ATPase within, the extramitochondrial space. It is shown that ADP formation in the mitochondrial intermembrane space is a prerequisite for a dominating oxidative phosphorylation in reconstituted systems, suggesting dynamic ADP compartmentation in that space.

Adenosine Diphosphate↗
PubMed1991

The effect of spacing repetitions on the recognition memory of young children and adults.

In Experiment 1, preschoolers, first graders, and third graders were presented a list of pictures that included twice-presented items separated by varying numbers of intervening items. Performance on a subsequent recognition test improved as the spacing between repetitions increased, but the effect of spacing did not interact reliably with grade level. In Experiment 2a, we replicated the spaced-repetition effect in young children and found a similar effect in college students. In Experiment 2b, we varied the conditions under which lists were presented to college students and again found a spacing function that was comparable to that of very young children. The results are consistent with the hypothesis that spaced-repetition effects in recognition are produced by fundamental memory mechanisms that are operational at a very early age and which undergo little change with development.

Adult↗
PubMed1985

Comparison of internal escape channels with die spacing and occlusal venting.

The effectiveness of the following procedures in improving the seating of full cast crowns were compared: internal escape channels, die spacing, occlusal venting, and a combination of die spacing with an escape channel. All techniques were shown to be similar in effectiveness. Die spacing produced the least consistent results. An internal escape channel, occlusal venting, die spacing, or a combination of an escape channel and die spacing did not influence the retention of full cast crowns.

Cementation↗
PubMed1987

The coronomaxillary space: literature review and anatomic description.

The dental literature has used a variety of terms to describe the distal buccal boundaries of the maxillae. The coronomaxillary space has been suggested as a more consistent descriptive term. It has been noted in the literature that this space narrows on mandibular opening. However, some authors recommend that overfilling this space aids retention. Explanations for this seeming contradiction in opinions have been suggested: In individuals with straight coronoid processes, the space can narrow on opening. The coronomaxillary denture may have to be thinned to maintain retention in function. In individuals with flared coronoid processes, the space can widen or remain constant on opening. The denture borders may have to be widened in contour to achieve retention.

Dental Arch↗