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PubMed2001

Aeration and drainage pathways of Prussak's space.

OBJECTIVE: the purpose of this study was to document the aeration and drainage pathways of Prussak's space. METHODS: 55 temporal bones with an age range from neonate to 11 years of age were serially sectioned to 20 microns, every 10th section was saved and stained by Hematoxylin eosin. Each consecutive section was studied as to the connections of Prussak's space to adjacent compartments and measurements of the dimensions were made for both Prussak's space and its aeration pathways. RESULTS: the classic aeration pathway via the posterior pouch, as described by Prussak in 1867, was found in 34 ears (62%). In 19 (36%), aeration occurred superior to the posterior pouch in the region of the lower lateral attic and the upper mesotympanum. In these ears the posterior pouch had formed, but its superior limit ended blindly in the tympanic membrane. In two temporal bones the aeration pathway was from the anterior pouch and in these cases also a blind posterior pouch had developed. In one temporal bone an auxiliary pathway in addition to the route via the posterior pouch was through the roof (the lateral malleal ligamental fold) of Prussak's space to the overlying lateral malleal space. The height of the posterior pouch varied with a range from 0.5 to 2.4 mm, and the greatest width, which was towards the posterior tympanic spine, varied from 1.6 to 3.2 mm. The superiorly blind posterior pouch was shorter, ranging from 0.4 to 1.2 mm in height. The most frequent route of the chorda tympani nerve was running from 0.5 to 1 mm medial to the posterior malleal ligament in the anterior half of the pouch, joining it posteriorly, or it was connected to it by a short fold, 37 ears (67%). In 18 cases (33%) the chorda was surrounded by its own fold, thus entirely separate from the posterior malleal ligamental fold during its entire course across the tympanum. CONCLUSIONS: we have made a detailed documentation of the aeration and drainage pathways of Prussak's space and the findings concur, with important modifications, with Prussak's original description. There is no evidence for contemporary claims that Prussak's space would be aerated superiorly between the lateral incudal and malleal folds. Prussak's space and its aeration pathway is an unit of its own, entirely separate of the major epitympanic compartments which are aerated via the tympanic isthmus. Due to frequent disease processes in the lower lateral attic and posterior mesotympanum, Prussak's space and its aeration pathway are likely to become blocked. This may lead to obliteration of Prussak's space and to the development of retraction pocket or papillary ingrowth cholesteatoma.

Child↗

PubMed2001

The relationship between soft tissue swelling, joint space narrowing and erosive damage in hand X-rays of patients with rheumatoid arthritis.

OBJECTIVES: To test the hypotheses that the progression of joint space narrowing behaves differently from the progression of erosions and that clinically and radiologically assessed soft tissue swelling relates more to diffuse cartilage loss than to erosive damage. METHODS: Radiographs and clinical data were obtained from 28 patients in a prospective, multicentre, randomized, placebo-controlled trial of prednisolone 7.5 mg daily over 2 yr. Radiographic scoring included the Larsen score, joint space narrowing and soft tissue swelling. Clinical joint inflammation in the hands was assessed every 3 months and cumulative synovitis score over the period of study was then calculated for each joint. The placebo-treated patients and the prednisolone-treated patients were analysed separately. The Larsen scores were compared after log transformation [transformed score=log(10) (original score+1)]. Changes in Larsen scores and joint space narrowing scores were compared with the cumulative presence of clinical synovitis and radiological soft tissue swelling using the correlation coefficient. RESULTS: There was a difference in the rate of progression in the Larsen score between placebo- and prednisolone-treated patients, but there was no significant difference in the rate of joint space loss. In placebo-treated patients, measures of synovitis correlated more strongly with progression of joint space narrowing than with changes in the Larsen score. In prednisolone-treated patients there was no correlation between clinical synovitis and change in Larsen score (r=0.029) and only a slight and non-significant correlation with joint space narrowing (r=0.127). Radiographic evidence of soft tissue swelling remained correlated with joint space narrowing (r=0.279, P:<0.001) but was not correlated with change in Larsen score (r=-0.113, P:<0.001 for difference between correlations). The correlation between Larsen score progression and joint space narrowing seen in the non-treated patients was completely abolished in the glucocorticoid-treated group (r=-0.003). CONCLUSIONS: The progression of joint space narrowing behaves differently from the progression of erosions. Prednisolone slows (or even stops) the progression of erosions (as assessed by the Larsen score) while making no difference to the progression of cartilage loss (as assessed by joint space narrowing). The results also suggest that synovitis, whether measured clinically or radiologically, is more closely related to diffuse cartilage loss than to erosion progression. Any link between synovitis and erosions is abolished by glucocorticoid therapy while the link between synovitis and cartilage loss is not, pointing to at least two different mechanisms for these observed radiological features.

Adolescent↗

PubMed2000

Cervical intervertebral disc space narrowing and size of intervertebral foramina.

Computer-assisted simulation of C4-C5, C5-C6, and C6-C7 intervertebral disc space narrowing was performed on 16 anatomic specimen cervical spines to determine the relationship of the cross sectional foraminal areas with the degree of narrowing of the cervical intervertebral disc space. Compared with normal foraminal area values, reduction of 20% to 30% of the foraminal area was found after 1 mm narrowing of the intervertebral disc spaces; reduction of 30% to 40% of the foraminal area was found after 2 mm narrowing of the intervertebral disc space; and reduction of 35% to 45% of the foraminal area was found after 3 mm narrowing of the intervertebral disc space. Statistically significant differences were found among the remaining cross sectional foraminal areas after different degrees of intervertebral disc space narrowing. Compression of the nerve root within the intervertebral foramina after the collapse of the intervertebral disc space cannot be ignored, and an appropriate surgical procedure to maintain the normal height of the disc space is essential. The size of the intervertebral foramen is related directly to the height of the intervertebral disc space. A 3-mm vertical reduction of the intervertebral disc space is associated more frequently with severe narrowing of the neuroforamen.

Aged↗

PubMedDate not supplied

Odontogenic versus nonodontogenic deep neck space infections: CT manifestations.

PURPOSE: The purpose of this study was to evaluate deep neck space infection (DNSI) with particular attention to the differences in the spaces involved and in complications between odontogenic and nonodontogenic groups with CT. METHOD: Forty-four patients (21 odontogenic and 23 nonodontogenic) were included in this study. Among odontogenic DNSI cases, 15 had dental infection in the second or third mandibular molar. We compared the CT features between odontogenic and nonodontogenic DNSI cases, with special emphasis on the differences in the spaces involved and in the rate and type of complications. RESULTS: In all patients, CT clearly differentiated abscess from cellulitis. The most common spaces involved in 21 patients with odontogenic DNSI were the parapharyngeal (n = 18), the submandibular (n = 18), the anterior visceral (n = 13), the masticator (n = 9), and the sublingual (n = 7) spaces. In contrast, in 23 patients with nonodontogenic DNSI, the anterior visceral space (n = 14) was most frequently involved. The parapharyngeal, submandibular, and masticator spaces were statistically more frequently involved in odontogenic than in nonodontogenic DNSI (p < 0.05). Twenty-two patients had one or more complications shown by CT, of which airway compromise was more frequent and severe in odontogenic than in nonodontogenic DNSI. CONCLUSION: We conclude that the parapharyngeal, submandibular, and masticator spaces are more significantly vulnerable in odontogenic DNSI than in nonodontogenic DNSI. The predilection for certain spaces of the neck in odontogenic DNSI seems to originate from the intimate relationship of the mandibular molars to the adjacent deep neck spaces.

Abscess↗

PubMed1994

An analysis of extradural dead space after fronto-orbital surgery.

This study was undertaken to evaluate several concerns regarding the extradural space resulting from elective fronto-orbital advancement or frontal sinus cranialization techniques. The questions are (1) Do infants undergoing these techniques have the potential to obliterate this space at an accelerated rate, e.g., within 1 or 2 days? (2) Do adults have any potential to obliterate the space? (3) Do children obliterate the space like infants or like adults? (4) What is the specific time sequence for dead-space obliteration? Twenty patients ranging in age from 6 months to 35 years were studied before and after fronto-orbital advancement. The patients were divided into three groups: (1) infants (up to 15 months), (2) children (up to 9 years), and (3) adults (9 years and beyond). Postoperative intracranial dead space was assessed by serial CT scans. Ten patients had CT scans more than 14 days after surgery. These data demonstrate that intracranial dead space in infants is obliterated in a delayed fashion. Children tend to obliterate intracranial dead space in a manner similar to that of infants. Adults are able to obliterate the space over a longer, but finite, period of time as compared with infants and children. Part of the mechanism responsible for obliteration of the postoperative space may be enlargement of the ventricular system.

Adolescent↗

PubMed2002

Neural space integrity of the lower cervical spine: effect of normal range of motion.

STUDY DESIGN: An experimental investigation of intervertebral foramen and spinal canal neural space integrity was performed throughout physiologic range of motion of the lower cervical spine in intact human cadaver specimens. OBJECTIVE: To investigate cervical positions that might place the neural tissues of the spine in heightened risk of injury. To meet this objective the following hypotheses were tested: 1) spinal canal integrity varies with specific normal range of motion positions of the lower cervical spine, and 2) intervertebral foramen integrity is dependent on and unique for different physiologic positions of the lower cervical spine. SUMMARY OF BACKGROUND DATA: Cervical spine injuries are frequently associated with compressive damage to neurologic tissues and consequently poor clinical outcomes. Neurologic injury typically occurs from disc, ligamentous, or bony occlusion of the spinal canal and intervertebral foraminal spaces dynamically during an injury event or with abnormal alignment and position after the injury event. Prior studies have shown pressure and geometric changes in cervical spine neural spaces in certain cervical spine positions. However, to the authors' knowledge, this is the first research effort aimed at elucidating the integrity of the cervical spine neural spaces throughout the normal physiologic range of motion. METHODS: The authors instrumented 17 fresh-frozen unembalmed cadaveric human cervical spines (C3-C7) with specially designed intervertebral foramen occlusion transducers and a spinal canal occlusion transducer. The specimens were loaded with pure bending moments to produce simulated physiologic motions of the lower cervical spine. The resulting occlusion profiles for the intervertebral foramen and spinal canal were recorded along with the 6-degree of freedom position of the cervical spine. Because these occlusion measurements describe the ability of the spine to preserve the space for the neural structures, the authors define this neuroprotective role of the vertebral column as neural space integrity. RESULTS: The range of motion developed experimentally in this study compared well with published reports of normal cervical motion. Thus, subsequent changes in neural space integrity may be regarded as resulting from normal human cervical spine motion. No significant change in the spinal canal space was detected for any physiologic motion; however, intervertebral foramen integrity was significantly altered in extension, ipsilateral bending, combined ipsilateral bending and extension, and combined contralateral bending with extension when compared with intact upright neutral position. CONCLUSIONS: This study defines the range of neural space integrity associated with simulated physiologic motion of the lower cervical spine in an experimental setting. This information may be useful in comparing neural space changes in pathologic conditions and may enhance refinement of neurologic injury prevention strategies.

Biomechanical Phenomena↗

PubMed2006

Effect of the increase in the height of lumbar disc space on facet joint articulation area in sagittal plane.

STUDY DESIGN: Computerized tomography (CT) of the lumbar spine cadaveric specimens was used to evaluate the effect of increasing the height of the disc space in the lumbar spine to the facet joint articulation in the sagittal plane. OBJECTIVE: To show how the facet joint articulation is affected by increasing the height of the disc space in the lumbar spine. SUMMARY OF BACKGROUND DATA: The Charité Artificial Disc (DePuy Spine, Inc., Raynham, MA) was successful in relieving low back pain in the majority of patients, yet there was still a significant number of patients who did not obtain pain relief, or their pain even worsened. The etiology of their pain is still not known. To our knowledge, no study has addressed the effect on the facet joints when the disc height is increased. METHODS: CT images passing through the center of the L3-S1 facet joints (sagittal plane) were obtained from 15 cadaveric lumbar spine specimens. The articulation overlap of facet joints in sagittal plane from the L3 to S1 was measured. A 1-mm incremental increase to a total 5 mm in disc space height was performed to simulate the changes seen in disc replacement. The change in the facet joint articulation overlap in sagittal plane at normal and each displacement was then measured. There were 5 lumbar spine specimens dissected to validate the technique and standardize the measurements. Mean, percentages, and standard deviation values were calculated for all measured dimensions. RESULTS: No significant difference was found between the measurements on CT and gross specimens (P > 0.05). In 15 specimens, the mean facet joint articulation overlap on the sagittal plane was: 16.29 +/- 1.20 mm (left) and 16.22 +/- 1.16 (right) at the L3-L4 level; 17.81 +/- 1.18 mm (left) and 17.74 +/- 1.18 mm (right) at the L4-L5 level; and 18.18 +/- 1.18 mm (left) and 18.23 +/- 1.15 mm (right) at the L5-S1 level. There is no significant difference between the measured values on left and right sides (P > 0.05). Each 1-mm incremental increase in disc space at the L3-L4 level translated to a decrease in the facet joint articulation overlap in the sagittal plane by 6%, and the mean facet joint space increased 0.4 mm. At the L4-L5 level, the articulation overlap decreased by 6%, and the facet joint space increased 0.5 mm. At the L5-S1 level, the articulation overlap decreased by 4%, and the facet joint space increased 0.7 mm. CONCLUSIONS: There is a significant decrease of the facet joint articulation overlap in sagittal plane and an increase in the facet joint space following an increase in the lumbar disc space. The inappropriate increase of the height of disc space will result in facet joint subluxation.

Humans↗

PubMed2001

A k-space method for large-scale models of wave propagation in tissue.

Large-scale simulation of ultrasonic pulse propagation in inhomogeneous tissue is important for the study of ultrasound-tissue interaction as well as for development of new imaging methods. Typical scales of interest span hundreds of wavelengths; most current two-dimensional methods, such as finite-difference and finite-element methods, are unable to compute propagation on this scale with the efficiency needed for imaging studies. Furthermore, for most available methods of simulating ultrasonic propagation, large-scale, three-dimensional computations of ultrasonic scattering are infeasible. Some of these difficulties have been overcome by previous pseudospectral and k-space methods, which allow substantial portions of the necessary computations to be executed using fast Fourier transforms. This paper presents a simplified derivation of the k-space method for a medium of variable sound speed and density; the derivation clearly shows the relationship of this k-space method to both past k-space methods and pseudospectral methods. In the present method, the spatial differential equations are solved by a simple Fourier transform method, and temporal iteration is performed using a k-t space propagator. The temporal iteration procedure is shown to be exact for homogeneous media, unconditionally stable for "slow" (c(x) < or = c0) media, and highly accurate for general weakly scattering media. The applicability of the k-space method to large-scale soft tissue modeling is shown by simulating two-dimensional propagation of an incident plane wave through several tissue-mimicking cylinders as well as a model chest wall cross section. A three-dimensional implementation of the k-space method is also employed for the example problem of propagation through a tissue-mimicking sphere. Numerical results indicate that the k-space method is accurate for large-scale soft tissue computations with much greater efficiency than that of an analogous leapfrog pseudospectral method or a 2-4 finite difference time-domain method. However, numerical results also indicate that the k-space method is less accurate than the finite-difference method for a high contrast scatterer with bone-like properties, although qualitative results can still be obtained by the k-space method with high efficiency. Possible extensions to the method, including representation of absorption effects, absorbing boundary conditions, elastic-wave propagation, and acoustic nonlinearity, are discussed.

Adipose Tissue↗

PubMed1986

Extraperitoneal paravesical spaces: CT delineation with US correlation.

The extraperitoneal space around the urinary bladder is lamellate, just like the retroperitoneal space around the kidneys. The bladder, urachus, and obliterated umbilical arteries lie within the perivesical space, surrounded by umbilicovesical fascia, analogous to the perinephric space within the renal fascia. A much larger prevesical space, analogous to the anterior pararenal space, lies anterior and lateral to the umbilicovesical fascia. Posterior to the urinary bladder, the lower uterine segment or seminal vesicles lie within the perivesical space, rather than in a separate compartment, corresponding to the posterior pararenal space. The cul-de-sac, and the inferolateral extension of its peritoneal layers as the rectovaginal or rectovesical septum, separate the posterior perivesical space from the rectum. The sectional anatomy of these spaces, and particularly their computed tomographic and ultrasound appearances, were noted in normal anatomic sections, patients with extraperitoneal fluid collections, and a cadaver into which fluid was injected.

Abdominal Muscles↗

PubMed1993

Effect of ventilation frequency and tidal volume on pleural space thickness in rabbits.

The thickness of the pleural space was measured by fluorescence video-microscopy during mechanical ventilation in anesthetized paralyzed rabbits. A transparent parietal pleural window was made in the fourth or sixth intercostal space near midchest by dissection of intercostal muscle and endothoracic fascia. Fluorescence-labeled (fluorescein isothiocyanate) dextran solution (1 ml) was injected into the pleural space via a rib capsule and allowed to mix with the pleural liquid. With the rabbit in the left lateral decubitus position and the pleural window superior, the light emitted from the pleural liquid through the pleural window was measured through the videomicroscope. Both ventilation frequency and tidal volume were varied. Pleural space thickness was determined by in vitro calibration of the pleural liquid at the end of the experiment. At a frequency of 40 breaths/min and a tidal volume of 20 ml, pleural space thickness averaged 35 +/- 15 (SD) microns (n = 7). When frequency was reduced to 8 breaths/min, this value was reduced by 40% to 22 +/- 11 microns. A reduction in tidal volume from 20 to 6 ml at a frequency of 40 breaths/min produced a similar reduction in pleural space thickness. During apnea, pleural space thickness averaged 11 +/- 3 microns. Cardiogenic motion had no measurable effect on pleural space thickness. The increased pleural space thickness with ventilation might serve to reduce the power dissipated due to sliding of the lung relative to the chest wall. Results support the concept of lubrication as the primary function of the pleural space.

Animals↗

PubMed2005

A suite of methods for representing activity space in a healthcare accessibility study.

BACKGROUND: "Activity space" has been used to examine how people's habitual movements interact with their environment, and can be used to examine accessibility to healthcare opportunities. Traditionally, the standard deviational ellipse (SDE), a Euclidean measure, has been used to represent activity space. We describe the construction and application of the SDE at one and two standard deviations, and three additional network-based measures of activity space using common tools in GIS: the road network buffer (RNB), the 30-minute standard travel time polygon (STT), and the relative travel time polygon (RTT). We compare the theoretical and methodological assumptions of each measure, and evaluate the measures by examining access to primary care services, using data from western North Carolina. RESULTS: Individual accessibility is defined as the availability of healthcare opportunities within that individual's activity space. Access is influenced by the shape and area of an individual's activity space, the spatial distribution of opportunities, and by the spatial structures that constrain and direct movement through space; the shape and area of the activity space is partly a product of how it is conceptualized and measured. Network-derived measures improve upon the SDE by incorporating the spatial structures (roads) that channel movement. The area of the STT is primarily influenced by the location of a respondent's residence within the road network hierarchy, with residents living near primary roads having the largest activity spaces. The RNB was most descriptive of actual opportunities and can be used to examine bypassing. The area of the RTT had the strongest correlation with a healthcare destination being located inside the activity space. CONCLUSION: The availability of geospatial technologies and data create multiple options for representing and operationalizing the construct of activity space. Each approach has its strengths and limitations, and presents a different view of accessibility. While the choice of method ultimately lies in the research question, interpretation of results must consider the interrelated issues of method, representation, and application. Triangulation aids this interpretation and provides a more complete and nuanced understanding of accessibility.

Journal Article↗

PubMed1998

Tissue and whole-body extracellular, red blood cell and albumin spaces in the rainbow trout as a function of time: a reappraisal of the volume of the secondary circulation

[58Co]EDTA, [51Cr]RBC and [125I]albumin spaces in the whole body and 28 tissue samples were examined at timed intervals over 16 h in rainbow trout Oncorhynchus mykiss. [58Co]EDTA space (which approximates extracellular fluid volume; ECF) in fins, skin, gallbladder and eye are reported for the first time. After a 16 h equilibration, ECF volume was large (376-726 microl g-1 wet tissue mass) in kidney, swimbladder, skin and fins, moderate (219-313 microl g-1 wet tissue mass) in stomach, skull, spleen, liver, intestine, gills, eye and cecum, and small (53-181 microl g-1 wet tissue mass) in red muscle, fat, brain, gallbladder and white muscle. Whole-body ECF was 387+/-10.6 microl g-1 (mean +/- s.e.m.; N=11). [51Cr]RBC space relative to [58Co]EDTA space was large in spleen, liver, intestine and gill, and low in skin, fins, stomach and skull. Whole-body [51Cr]RBC space was 9.9+/-0.6 microl g-1 body mass (N=17). Blood volume calculated from [51Cr]RBC space at 16 h and a dorsal aortic hematocrit of 24.5 % was 40.4 microl g-1 body mass. Whole-body [125I]albumin space at 16 h was 118.0+/-7.4 microl g-1 body mass (N=6), which resulted in an estimated blood volume of 156. 6 microl g-1 body mass, nearly four times that estimated from the [51Cr]RBC space. Tissue hematocrits, calculated from [125I]albumin and [51Cr]RBC spaces, were significantly lower than dorsal aortic hematocrit in all tissues except spleen, kidney and liver. [58Co]EDTA and [51Cr]RBC spaces reached equilibrium in nearly all tissues within 1 h, whereas [125I]albumin continued to accumulate in many tissues up 24 h. The disparity between [125I]albumin distribution kinetics compared with the kinetics of [58Co]EDTA and [51Cr]RBC distribution, as well as the accumulation of [125I]albumin in tissues not known to have a secondary circulation, indicates that [125I]albumin is a poor marker of plasma volume in trout and that previous studies based on [125I]albumin clearance from the plasma have overestimated both the volume and the turnover rate of the secondary system. Revised estimates of secondary circulation volume, based on [58Co]EDTA distribution rate, indicate that it is no more than 10-20 % of the volume of the primary circulation.

Journal Article↗

PubMed2000

Effects of word spacing on reading Chinese text from a video display terminal.

This study investigated the effects of designing space between words in Chinese text, i.e., whether using a "word" instead of a "character" as a presentation unit, will facilitate the performance of reading from a video display terminal. Experimental results indicated that the main effect of word spacing significantly affected the reading time and the number of questions answered correctly. Subjects spent less time on the text with half-character word spacing or with whole-character word spacing than with conventional type (without word spacing). We also discovered that the number of questions answered correctly for stimuli with half-character spacing is significantly greater than that for stimuli with whole-character spacing, while both are smaller than for stimuli with conventional type. The additional variables, such as text difficulty and display control have significant effects as well. Our results suggested that the optimal word spacing in Chinese text should be greater than that in the traditional layout and less than a whole-character spacing. Apparently, in Chinese text, using a "word" as a presentation unit is more favorable than the traditional layouts that do not have any explicit word boundaries. The word spacing design may benefit in reading difficult or unfamiliar materials and further apply in emergency situations or in reading ambiguous sentences.

Adult↗

PubMed1997

Changes in airway space following mandibular setback using sagittal split osteotomy and rigid internal fixation.

The changes in airway space following mandibular setback using sagittal split osteotomy and rigid internal fixation were studied in 28 Japanese patients with mandibular prognathism. The correlation between the amount of mandibular setback and airway space changes, as well as the correlation between the amount of airway space changes and relapse of pognion point during the following-up period were also studied. Lateral cephalometric radiographs were taken immediately before and shortly after surgery as well as 5 to 12 months postoperation. The cephalometric evaluations of airway space width and area were based on stable craniofacial landmarks. The mean setback of mandible was 8.3 mm in the right side, and 8.2 mm in the left side. The mean amount of relapse of pogonion point during the following-up period was 0.52 mm horizontally, and 0.92 mm vertically. A significant decrease in airway space width and area, especially in the lower part of airway space was found following mandibular setback shortly after surgery. Although there was some increase both in airway space width and area during the following-up period, they did not increase to their original values. This suggests that the narrowing of airway space following mandibular setback using sagittal split osteotomy can be permanent. No significant correlation was found between the amount of mandibular setback and airway space changes. Since the relapse of pogonion point during the following-up period was too small, there is no significant correlation between it and the amount of airway space changes.

Adolescent↗

PubMed2002

Congruent qualitative behavior of complete and reconstructed phase space trajectories from biomolecular dynamics simulation.

Central to the study of a complex dynamical system is knowledge of its phase space behavior. Experimentally, it is rarely possible to record a system's (multidimensional) phase space variables. Rather, the system is observed via one (or few) scalar-valued signal(s) of emission or response. In dynamical systems analysis, the multidimensional phase space of a system can be reconstructed by manipulation of a one-dimensional signal. The trick is in the construction of a (higher-dimensional) space through the use of a time lag (or delay) on the signal time series. The trajectory in this embedding space can then be examined using phase portraits generated in selected subspaces. By contrast, in computer simulation, one has an embarrassment of riches: direct access to the complete multidimensional phase space variables, at arbitrary time resolution and precision. Here, the problem is one of reducing the dimensionality to make analysis tractable. This can be achieved through linear or nonlinear projection of the trajectory into subspaces containing high information content. This study considers trajectories of the small protein crambin from molecular dynamics simulations. The phase space behavior is examined using principal component analysis on the Cartesian coordinate covariance matrix of 138 dimensions. In addition, the phase space is reconstructed from a one dimensional signal, representing the radius of gyration of the structure along the trajectory. Comparison of low-dimensional phase portraits obtained from the two methods shows that the complete phase space distribution is well represented by the reconstruction. The study suggests that it may be possible to develop a deeper connection between the experimental and simulated dynamics of biomolecules via phase space reconstruction using data emerging from recent advances in single-molecule time-resolved biophysical techniques.

Animals↗

PubMedDate not supplied

Comparison of two methods of space prediction in the mixed dentition.

PURPOSE: This study compares the accuracy of space prediction for the unerupted permanent canines and premolars by a recognized method of mixed dentition space analysis (Moyers technique) vs estimation by simple visual observation (SVO). METHODS: Twenty clinicians with varying levels of dental experience and training blindly assessed study models of 4 intact arches (2 maxillary and 2 mandibular) from 3 patients in the mixed dentition using both Moyers and SVO space prediction methods. Corresponding full-mouth panoramic radiographs were available for each case. Follow-up records of the eventual outcome in the permanent dentition for each case available (ie, study models prior to any form of orthodontic intervention) served as the standard for further comparison of the space predictions made. Predictions by both methods were compared with each other as well as with the eventual space situation in the permanent dentition. RESULTS: The differences in overall mean space prediction between the Moyers technique (excluding molar shift) and SVO ranged between 3.67 mm to 6.9 mm (lower arches) and 4.3 mm to 4.8 mm (upper arches). Diagnostic consistency between both methods' predictions was highly variable, with correlation ranging from moderate (r = 0.53, P = .01) to very weak (r = -0.1). Generally, more crowding was estimated with the SVO method's predictions. However, the inclusion of molar shift in the Moyers analysis resulted in the prediction of more crowding in the mandible compared to SVO and eventual outcome in the permanent dentition. The range and variability in predictions were always smaller with the Moyers technique compared to SVO. Neither technique's mean space prediction more closely resembled the eventual space situation in the permanent dentition. CONCLUSIONS: This study demonstrated that although the Moyers technique demonstrated less variation and more reproducibility than SVO in its space predictions, neither of the techniques was any more accurate in predicting the final space outcome in the permanent dentition.

Analysis of Variance↗

PubMed1991

Comparison of the width of the intervertebral disk space and radiographic changes before and after intervertebral disk fenestration in dogs.

Intervertebral disk space widths were measured on lateral radiographs of 73 anesthetized dogs. Weight was found to have a significant (P less than 0.01) effect on disk space width. Using weight-adjusted disk space width measurements for all subsequent studies, older (7- to 16-year-old) dogs and males had consistently, but not significantly, wider, disk spaces than did alternative groups. Cervical and lumbar intervertebral disk spaces tended to be wider than those in the caudal thoracic region. The widest cervical intervertebral disk spaces were C4-5 and C5-6 and the narrowest was C2-3. In the lumbar region, L2-3 was the widest disk space and L4-5 was the narrowest. Dachshunds generally had greater mean intervertebral disk space width than did other breeds of dogs. Cervical (n = 6 dogs) and thoracolumbar (n = 6 dogs) disk fenestration resulted in narrow intervertebral disk spaces, regardless of breed. When a ventral approach was used in thoracolumbar fenestration, the mean intervertebral disk space was narrower than that resulting from use of a dorsolateral approach. Spondylosis was found radiographically 1 to 4 years after intervertebral disk fenestration in 3 of 6 dogs that had cervical fenestrations and in 5 of 6 dogs that underwent thoracolumbar fenestration.

Age Factors↗

PubMedDate not supplied

Urea, creatinine, uric acid, and phosphate spaces and their relationship to total body water during chronic hemodialysis.

The authors determined total body water (TBW) with tritium in 11 patients on chronic hemodialysis and compared this space to that estimated by 60% of body weight, and removal spaces of urea, creatinine, uric acid, and phosphate (PO4). The latter spaces were determined by dividing the total amount of substance (measured in total dialysate) by pre- minus post-dialysis concentrations. Body water X 0.6 was more than 10% less than the tritium space, and showed a maximal variation of 10 liters, or 24%. The removal space of urea was 80% of the tritium space, but correlated closely with it. The difference between total body water and urea removal space was variable and dependent on fluid excess (edema) in the patients. Creatinine, uric acid, and phosphate removal spaces were highly variable and not correlated to total body water. The authors suggest that actual measured TBW should be used, rather than estimations using BW X 0.6, for V in K X T/V, where K = clearance, T = duration of dialysis, and V = the removal space of urea. Furthermore, one may need to introduce a correction factor for urea removal space over TBW in the equation to allow better quantification of dialysis in edematous patients and during very fast dialyses.

Adult↗