Right-left Symmetry Research Articles

Geometric parameters of the in vivo tissues at the lumbosacral joint of young Asian adults.

Magnetic resonance images (MRIs) were used to determine the geometry of the tissues studied. To investigate the geometric parameters of tissues around the lumbosacral joint. Cross-sectional area (CSA), moment arms, and line of action of the tissues located at lumbosacral joint (L5-S1), which are important in the study of spinal mechanics and models for the investigation of low back pain. It was insufficient information to describe the relative dimension of spinal tissues except muscles around the lumbar spine. MRIs from eight asymptomatic young Taiwanese male adults were collected to present CSA, moment arms, and line of action of the tissues located at lumbosacral joint (L5-S1). Four pairs of trunk muscles, erector spinae, rectus abdominis, abdominal oblique externus, and psoas muscles, ligamentum flavum, and facet joints at the bilateral sides were studied. Spinal tissues at the level of lumbosacral joint were determined. The CSAs of the spinal elements at the L5-S1 normalized by the CSA of trunk ranged from 5.42% (the erector spinae) to 0.14% (the ligamentum flavum). The moment arm of the spinal elements relative to the trunk width and depth ranged from 40.91% (rectus abdominis at the y direction) to 0.38% (ligamentum flavum at the x direction). The profile of geometric elements of lumbosacral joint in the Asian male subjects was similar to the data collected from the white population. The data also showed that right-left symmetry in the aforementioned dimension. Normalized data of the CSA, moment arm, and line of action of the spinal tissues at the L5-S1 joint were reported in vivo through the MRI techniques. The profile of geometric elements of lumbosacral joint in the Asian male subjects did not differ from the white population. In addition to muscles, the geometry of facet joint and ligament was determined, which would be important to the calculation of force distribution on the lumbosacral joint.

A procedure to average 3D anatomical structures

Creating a feature-preserving average of three dimensional anatomical surfaces extracted from volume image data is a complex task. Unlike individual images, averages present right-left symmetry and smooth surfaces which give insight into typical proportions. Averaging multiple biological surface images requires careful superimposition and sampling of homologous regions. Our approach to biological surface image averaging grows out of a wireframe surface tessellation approach by Cutting et al. (1993). The surface delineating wires represent high curvature crestlines. By adding tile boundaries in flatter areas the 3D image surface is parametrized into anatomically labeled (homology mapped) grids. We extend the Cutting et al. wireframe approach by encoding the entire surface as a series of B-spline space curves. The crestline averaging algorithm developed by Cutting et al. may then be used for the entire surface. Shape preserving averaging of multiple surfaces requires careful positioning of homologous surface regions such as these B-spline space curves. We test the precision of this new procedure and its ability to appropriately position groups of surfaces in order to produce a shape-preserving average. Our result provides an average that well represents the source images and may be useful clinically as a deformable model or for animation.

Right-left symmetry of aR ⊕ bR = ( a + b) R in regular rings

A somewhat surprising and unexpected result in the theory of von Neumann regular rings is proved.

Kinematic gait analysis of hind limb symmetry in dogs at the trot

Abstract Objective To describe intratrial differences in hind limb symmetry in healthy dogs at the trot, using non-invasive, computer-assisted, three-dimensional kinematic gait analysis. Animals 8 clinically normal large-breed adult dogs. Procedure Dynamic flexion and extension angles and angular velocities were calculated for the coxofemoral, femorotibial, and tarsal joints of dogs at the trot. Temporal and distance variables were computed. Essential Fourier coefficients were used to determine mean flexion and extension curves for all joints and to compare differences in movement between right and left hind limbs. Variances attributable to limb, dog, and trial were determined. Results Each joint had a characteristic pattern of flexion and extension movement that was used to compare intratrial symmetry of hind limb gait. Significant differences were not detected in temporal or distance variables between the right and left hind limbs. Significant differences were not noted in essential Fourier coefficients used to characterize coxofemoral, femorotibial, and tarsal joint angles and angular velocities, with the exception of the cosine-0 coefficient for coxofemoral angular velocity. Variation in joint angle and angular velocity measurements were attributable to individual dog and trial. Variation attributable to limb was negligible. Conclusions Intratrial evaluation of right-left hind limb symmetry, using kinematic gait analysis, indicated objectively that hind limb movement is symmetrical at the trot in healthy large-breed dogs. Clinical Relevance Documentation of hind limb symmetry at the trot will help provide a basis for direct comparison of both hind limbs in future studies evaluating gait and treatment of dogs with musculoskeletal disease. (Am J Vet Res 1998;59:680-685)

HMPAO spect brain imaging in treatment-resistant depression

1. 1. There is little published research on brain function in treatment-resistant depression (TRD). This study examined regional cerebral blood flow using 99mTechnetium-hexamethylpropanolamine oxime (HMPAO) single photon emission computed tomography in 8 patients with a history of TRD, 13 depressed patients without TRD (non-TRD) and 16 normal controls. 2. 2. Relative HMPAO activity in selected brain regions revealed a significant increase in hippocampus-amygdala activity in TRD patients compared to non-TRD patients and healthy controls. The mean value of relative HMPAO activity did not differ in any other brain region, nor were there any differences in right-left symmetry among the subject groups. 3. 3. The observation of increased hippocampus-amygdala HMPAO activity in TRD patients suggests that functional abnormalities in limbic circuitry may play a role in the pathophysiology of treatment-resistance.

Contrast enhancement of the facial nerve on MRI: normal or pathological?

We prospectively analysed the normal contrast-enhanced MRI features of the facial nerve and determined criteria for pathological contrast enhancement. We studied 31 patients with clinically normal facial nerves with T1-weighted images before and after contrast medium. The intensity, thickness and right-left symmetry of enhancement were assessed in each segment and correlated with MRI features observed in abnormal facial nerves. Enhancement along at least one segment of the facial nerve was seen in 98% of cases, but only within the facial canal: labyrinthine segment: 78.2%; geniculate ganglion: 96.9%; tympanic: 88.4%; mastoid: 66.6%. Marked (+2) to intense (+3) enhancement was seen in the labyrinthine segment in 17.4%, the geniculate ganglion in 36.3%, and the tympanic (25.6%) and mastoid (7.1%) segments, whereas intense enhancement was only seen in the geniculate ganglion (6%) and the tympanic segment (11.6%). A right-left asymmetry was noted in 69% of cases. No correlation was found between enhancement and the thickness of the nerve. No enhancement of the eighth nerve was seen. We suggest three criteria for pathological enhancement: enhancement outside the facial canal; extension of enhancement to the eighth nerve; and intense enhancement in the labyrinthine and/or mastoid segments.

Symmetry of projection in the quantitative analysis of mammographic images.

Mammographic parenchymal patterns are among the strongest indicators of the risk of developing breast cancer. Risk evaluation through breast patterns may have an important role in studies of the aetiology of breast cancer and for monitoring changes in the breast in evaluating potential risk-modifying interventions. Typically, patterns are assessed by an experienced radiologist according to Wolfe grade, or on a coarse quantitative scale according to percent density. Parenchymal characterization methods, to overcome variability of classification by human observer, are under investigation. These include image segmentation using semi-automatic thresholding and automatic classification through textural and density measures. An important practical question relates to the extent to which information about mammographic pattern is carried by any one of the four views obtained in a typical examination. Specifically, variations of right-left breast symmetry and variations between the two standard views of each breast were tested. The mammograms of 30 premenopausal women, comprising 90 images [30 each of the right cranial-caudal (RCC), left cranial-caudal (LCC) and right medial-lateral oblique (RMLO)] were evaluated. Parameters included both subjective (radiologist classification and interactive image thresholding) and objective (fractal and skewness indices) quantitative measurements of parenchymal pattern. For the parameters tested, a high degree of correlations was observed for measurements on the RCC, LCC and RMLO views. Pearson correlation coefficients between 0.86-0.96 were found for the comparisons of quantitative parameters. The strong correlations suggest that, in the study and application of mammographic density classification, representative information is provided in a single view.

Some principles in the dental crown construction in permanent maxillary centrals of Slovenians

To increase the understanding of the incisors crown form, the lingual fossa depth, crown width and crown thickness between lingual marginal ridges of the permanent maxillary centrals were measured on 257 stone casts of Slovene children. The right-left, male-female differences, as well as the correlations between the variables themselves were analysed. Male centrals exhibited wider and thicker crown compared to female centrals, while the lingual fossa depth showed no sex differences. A positive correlation in terms of positive allometry between lingual fossa depth and crown width was established. A negative lingual fossa depth-crown thickness correlation was found with female left centrals. High right-left symmetry was established, except for the directional asymmetry of all three measured variables on female centrals. The results indicate that the positive correlation in terms of positive allometry between the thickness of the lingual marginal ridges and the crown width is one of the basic principles of the crown formation for the permanent maxillary centrals. Usually we have to work with absolute thickening of the lingual marginal ridges because relative thickening on the account of the crown thickness is less usual. The latter possibility is less favourable for the firmness of the dental crown.

The geometry of the psoas muscle as determined by magnetic resonance imaging

Magnetic resonance images from fifteen physically active and asymptomatic male volunteers were collected to present morphometric parameters on the psoas and its moment arms, which are important in the study of spinal mechanics and models for the investigation of low back pain. The mean age of the subjects was 21.5 +/- 1.8 years. Data were obtained from nine vertebral and/or intervertebral levels (L2, L2/L3, L3, L3/L4, L4, L4/L5, L5, L5/S1, S1). In general, the psoas increased in size as it descended the trunk, moving anteriorly and slightly laterally in relation to the vertebral column. Maximum cross-sectional areas for the psoas (M = 16.3cm2) were observed at the L4/L5 level. Right-left symmetry was apparent in the aforementioned dimension, but not with respect to the mediolateral (X) diameter of the muscle. The length of the X moment arm was significantly (p < .05) greater for the right versus the left psoas from L3 to S1, with the length increasing as the psoas descended the trunk. However, this trend was not noted for the anteroposterior (Y) moment arm where observed values remained relatively small throughout the course of the muscle. These results will contribute to the study of low back pain onset and the design of appropriate rehabilitation interventions by providing accurate morphometric parameters for biomechanical models to predict of the loading conditions of the spine in vivo.

Spontaneous transitions and symmetry: Pattern dynamics in human four-limb coordination

Transitions between the coordinative patterns of rhythmically moving human arms and legs were studied to test the predictions of a four-component model (Schöner, Jiang and Kelso, 1990). Based upon results from previous two-component experiments (Kelso and Jeka, 1992), three assumptions were made about the four-limb system: (1) all limb pairs produce stable in-phase and anti-phase patterns; (2) the coupling between homologous limbs (i.e., right and left arms or right and left legs) is appreciably stronger than the coupling between nonhomologous limbs (i.e., arm and leg); and (3) right-left symmetry. An analysis of a four-component model (Jeka, Kelso and Kiemel, 1993) led to the prediction of four attracting invariant circles, each with two stable patterns in the state space of four-limb dynamics. In an experiment to test this prediction, subjects were required to cycle all four limbs in one of the eight patterns to the beat of an auditory metronome whose frequency was systematically increased. All subjects demonstrated spontaneous transitions corresponding to pathways along the invariant circles. Pre-transition relative phase variability increased with required frequency up to the transition, suggesting that loss of pattern stability induced the observed transitions. Thus, despite a large number of potential transitions, differential coupling between limb pairs and symmetry of the pattern dynamics restricts the behavior of the human four-limb system to a limited area of its state space.

Rapid semi-automated CT determination of ventricular area

200 phrenics showed a significantly greater than mean difference (1.83 1?1 1.85 versus 0.12 k 2.08 cm*, p = .02). No other significant differences emerged, due in part to the high degree of variance in the measures from slice A, as it is located near the poles of the temporal lobe. These results suggests that temporal lobe anatomical differences between schizophrenics and controls can be identified using MRI, that these structures differ in right-left symmetry, and that such asymmetries may be related to the neuropathology of schizophrenia. Further, this study is consistent with previous findings of abnormalities in the structure and function of the temporal lobe in schizophrenia. Further structural analyses will be presented.

The right-left symmetry axis of the brain on CT

The location of the brain's symmetry axis on computerized tomography (CT) images was mathematically formulated. A series of computer programs were written to “peel off” the skull and artifacts external to the skull. Image lines were then tested for right-left symmetry and in each line a pixel was selected which best represented the center of symmetry of the skull contents. The resultant calculated symmetry line of images with and without pathology was comparable to the visually determined symmetry axis. This method permits computed screening for right-left asymmetry.

An ear asymmetry for gap detection following anterior temporal lobectomy

A threshold elevation in the performance of auditory temporal order judgment in man has been reported in the ear contralateral to the side of an anterior temporal lobectomy. On the basis of temporal order judgments alone it is not possible to determine whether the deficit is attributable to an impairment of recognition, identification, or temporal resolution. The present monaural experiments compared the performance of the two ears in the detection of a gap in a broad-band noise burst in normal and temporal lobectomized subjects. The results revealed a right-left symmetry in gap detection performance by normal subjects but a significant deficit in gap detection in the ear contralateral to the side of an anterior temporal lobectomy—a finding interpreted as revealing the existence of a bonafide deficit in auditory temporal resolution induced by such resection.

Human plantar flexion strength and structure

Plantar flexion strengths were studied in 30 right-handed males. Static and dynamic maximum plantar flexion torques were recorded, knees fully extended (0 degrees) and in 90 degrees flexion. In five of the subjects the soleus and gastrocnemius muscle structure were studied by light microscopy and enzyme histochemistry. Specimens were obtained by needle biopsy, usually bilaterally. Intraindividual declines of force were found to be a function of angular motion velocity. Static and dynamic torques correlated significantly. Peak torques were significantly greater (mean 15%) at the 0 degrees than at the 90 degrees knee angle and left maximum plantar flexion torques at 0 degrees were greater (mean 10%) than right. Mean morphometric data on the m. soleus suggested right-left symmetry, which could not be demonstrated for the m. gastrocnemius. Fibres with low stainability for myofibrillar ATPase (Type 1 fibres) had smaller diameters, but constituted the major part of the cross-sectional areas. In these five non-athletes no significant correlation between data on plantar flexion strength and morphometric data on triceps surae structure could be demonstrated. On the other hand, strength covariated with calf circumference.

Right-left symmetry of flowers

The flowers of certain plants define a right or left handedness by the sense in which the petals are twisted. Some species and even entire families have flowers of only one particular handedness. There are also plants which produce right-handed as well as left-handed flowers in the same bloom. In the plants of themalvaceae family which belongs to this category, the probability of occurrence of flowers having a given handedness (right or left) undergoes time variations. The possible implications of the right-left symmetry problem of flowers is discussed.

Right-left symmetry preservation by flowers of malvaceae family

The flowers of malvaceae family preserves the symmetry between right and left in a peculiar manner. Plots belonging to this family bear two kinds of flowers, right-handed flowers with anticlockwise twisted petals and left-handed flowers with clockwise twisted petals. The branches of the plant prefers production of one type of flowers in excess of the other. There are two distinct types of branches, dextral branches and sinistral branches. Dextral (sinistral) branches produce more right-handed (left-handed) flowers than left-handed (right-handed) flowers. The average percentage of right-handed flowers in a dextral branch is same as that of left-handed flowers in a sinistral branch.

Mottled permanent incisors in 15‐year‐old Lagos children

Mottled permanent incisors were studied in a stratified convenience sample of 206 Lagos schoolchildren aged 15 years. The mouth prevalence of this condition was 32%, and the right-left symmetry of the mottled incisors occurred very approximately in only a third of those persons with mottling. The distribution pattern was similar to that observed in similarly aged children in non-fluoride communities, and also that observed in optimally fluoridated Anglesey, England. The cause of this type of mottling in unknown, but its distribution suggests that endogenous (possibly genetic) factors may be involved.

On Loewy length of rings

Associated with each ring R over which every nonzero right module has a minimal submodule is an ordinal number called its right (lower) Loewy length. The concern here is with the various possible left and right Loewy lengths of such rings with zero radical and with the possible right-left symmetry of this minimal submodule condition. In particular, if R has finite right Loewy length n then R has left Loewy length g 2n — 1. All rings are associative rings with identity. Denoting the socle of a module M by Soc (M), the (lower) Loewy series for M is defined transfinitely by: So = 0, Sa+JSa = Soc (M/Sa) and, if a is a limit ordinal, Sa = \Jβ<aSβ. (See Bass [1, p. 470].) If M = Sa for some ordinal number a then M is called a (lower) Loewy module. The Loewy length of such a module is L(M) = 7, the least ordinal 7 with M — Sr. We call a ring R a right (resp., left) Loewy ring in case the regular representation RR (resp., RR) is a Loewy module. (Nastasescu and Popescu [6] use the term semi-artinian to denote such a ring.) A ring R is easily seen to be a right Loewy ring if and only if each of its right modules has a nontrivial (hence, essential) socle. Over such a ring each right module M is a Loewy module of length L(M) ^ L(RR) and, since RR is finitely generated, L(RR) cannot be a limit ordinal.

The anatomical site distribution of clinical dental caries in the maxillary incisor teeth of 11- and 12-year-old children

The prevalence and selected aspects of the anatomical site distribution of dental caries in the maxillary incisor teeth of 11- and 12-year-old children are described. Data were obtained from two independent sources. An epidemiological study of 1246 boys and 1191 girls residing in the Leeds area constituted the first source. In this population of 2437 children, 560 (that is 23 per cent) had one or more DMF (including crowned) maxillary incisor teeth. The second source consisted of a survey carried out by school dental officers in the North of England (excluding the Leeds area) who recorded the anatomical site distribution of missing and carious teeth in 463 twelve-year-old children with DMF maxillary incisor teeth. It was found that the distribution of DMF maxillary incisor teeth among individuals is extremely non-random. Generally speaking, a high degree of right-left symmetry between affected teeth and affected sites (especially in central incisors) was observed in the population. In individuals, however, the frequency of asymmetrical attacks of caries at mesial, distal and lingual pit sites nearly always exceeded that of symmetrical attacks. Similarly, the frequency of single attacks at mesial and distal sites on adjacent maxillary incisor teeth, was greater than that of double attacks in which both mesial and distal sites were affected. Also, for a given tooth, unilateral lesions (mesial or distal surfaces) were much more common than bilateral ones (mesial and distal surfaces). The general features of the anatomical site distribution of dental caries in maxillary incisor teeth, broadly resemble those reported earlier in mandibular incisors, and it is concluded that they implicate an endogenous contribution to the multifactorial pathogenesis of dental caries.

Serologische untersuchungen zur struktur des tabakmosaikvirus

TMV shells which were free from nucleic acid were obtained by reaggregation of A-protein. It was possible to show by serological reactions at pH 5.6 (precipitation and absorption technique) that they possess the same antigen structure as the intact TMV. There were serological specificities on free A-protein which were lost after reaggregation and which were also absent from intact TMV. Thus they appear to be localised on those parts of the surface of the A-protein which were covered after reaggregation to the TMV shell. But on intact TMV and also on reaggragated A-protein we found a strong characteristic antigen component which is absent from free A-protein. This component must owe its specificity to the lines of contact between the A-protein particles which are combined to form the TMV shell. The newly formed bonds will be the basis for the additional specificity. Therefore the connections of the protein sub-units between the A-protein particles must be different from those within the A-protein. Provided that there is only one type of repeating sub-unit, this could be realised by assuming a mirror-like right-left symmetry in the double-peptide chains and in the A-protein as is schematically shown in Fig. 5.