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PubMed1999

Systematic noise compensation for simultaneous multislice acquisition using rosette trajectories (SMART).

Simultaneous multislice acquisition using rosette trajectories (SMART) is a recently introduced functional magnetic resonance imaging pulse sequence that offers high-speed data acquisition by simultaneously exciting several slices. A drawback to its benefit of rapid acquisition is the cumulative effect of the systematic noise present in the off-resonant slices. In this work, a systematic noise compensation method is implemented to gauge the performance of the multislice SMART method versus a single-slice rosette method in a motor activation study. The normalized standard deviation of the noise-compensated image timecourse is reduced by 25% (single-slice rosette) and 62% (SMART), and the normalized volume of motor activation is increased by 25% (single-slice rosette) and 44% (SMART). The noise-compensated SMART method has an average timecourse standard deviation only 9% higher than the noise-compensated single-slice rosette method, while increasing the acquisition rate threefold.

Artifacts↗

PubMed1999

Fast magnetic resonance coronary angiography with a three-dimensional stack of spirals trajectory.

In this work, three-dimensional (3D) spiral imaging has been utilized for magnetic resonance coronary angiography. Spiral-based 3D techniques can dramatically reduce imaging time requirements compared with 3D Fourier Transform imaging. The method developed here utilized a "stack of spirals" trajectory, to traverse 3D k-space rapidly. Both thick-slab volumes encompassing the entire coronary tree with isotropic resolution and thin-slab volumes targeted to a particular vessel of interest were acquired. Respiratory compensation was achieved using the diminishing variance algorithm. T2-prepared contrast was also applied in some cases to improve contrast between vessel and myocardium, while off-resonance blurring was minimized by applying a linear correction to the acquired data. Images from healthy volunteers were displayed using a curved reformatting technique to view long segments of vessel in a single projection. The results demonstrate that this 3D spiral technique is capable of producing high-quality coronary magnetic resonance angiograms.

Algorithms↗

PubMed2003

Convergence in peptide folding simulation: multiple trajectories of a potential AIDS pharmacophore.

To examine the conformational properties in aqueous solution of a 15-residue peptide that is a potential pharmacophore for AIDS vaccine development, molecular dynamics simulations were performed in water starting from structures determined experimentally in three different organic solvents. Convergence characteristics of the simulation are examined in Cartesian and conformational spaces. In addition, novel analysis tools are employed including a multidimensional scaling method to represent the distance between trajectory frames. As these methods are based on a variety of physical parameters, they provide a useful cross-check on the structural convergence. Theoretical two-dimensional (2D) 1H-NMR spectra are also generated. These are superficially quite different in appearance, demonstrating that backbone similarities difficult to identify by visual inspection of 2D NMR data can be revealed using the methods described here.

AIDS Vaccines↗

PubMed2004

Loss of Gli3 and Shh function disrupts olfactory axon trajectories.

The transcriptional regulator Gli3 and the secreted signal Shh influence induction, patterning, and differentiation at several sites of mesenchymal/epithelial (M/E) interaction including the limbs, heart, face, and forebrain. We asked whether loss of function of these two genes has specific consequences for early differentiation of the primary olfactory pathway-which comprises both craniofacial and forebrain structures and depends on M/E induction during initial stages of development. Loss of Gli3 or Shh function does not compromise several aspects of olfactory receptor neuron (ORN) and olfactory ensheathing cell maturation; however, directed outgrowth of ORN axons and their initial targeting to the telencephalon is altered. In Gli3 mutant extra toes-Jackson (Xt(J)Xt(J)) embryos, ORN axons defasciculate and project aberrantly near the forebrain. They rarely enter the central nervous system, and their association with mesenchymal laminin is disrupted. In Shh-/-embryos, ORN axons exit a single olfactory epithelium (OE) that develops centrally within an altered mesenchymal environment in a dysmorphic proboscis. These axons project as a single nerve toward the mutant forebrain; however, their trajectory varies according to the position of the proboscis relative to the forebrain. These alterations in axon outgrowth probably reflect compromised inductive interactions in the olfactory primordia because neither Gli3 nor Shh are expressed in olfactory neurons. Thus, two genes that influence induction and subsequent differentiation of craniofacial structures and the forebrain have distinct consequences for ORN axon growth during the initial genesis of the olfactory pathway.

Adaptor Proteins, Signal Transducing↗

PubMed1975

Reconstruction of axonal trajectory of individual neurons in the spinal cord using Golgi-stained serial sections.

A procedure bringing the axonal and dendritic cut ends found in the confronting planes of the serial sections face to face by means of serial photomicrographs provides a means for precisely reconstructing individual Golgiimpregnated neurons. Utilizing this method, it was possible to follow at the caudal level of a kitten's spinal cord the total course of the axons and dendrites of sixteen intramedullary neurons. The neurons located in the dorsal horn (laminae IV and V) send their long ascending axon into the lateral funiculus of the ipsi- or contralateral side, and, in one case, into the anterior funiculus of the ipsilateral side, giving off on the way several collaterals to the dorsal half of lamina VII of the ipsi- or contralateral side. Some of the neurons found in the intermediate region and the ventral horn (laminae VII, VIII and X) distribute their axonal branches in the intermediate region or the ventral horn of the ipsi- or contralateral side or both sides, running throughout their course in the grey matter, while the others act in the same manner by way of the lateral or anterior funiculi. Axonal and collateral endings terminate with small terminal knobs. The total axonal length of the neurons observed, with the exception of some with a long ascending trajectory, varies from 1,680 mum to 6,480 mum.

Animals↗

PubMed1978

Reconstruction of trajectory of primary afferent collaterals in the dorsal horn of the cat spinal cord, using Golgi-stained serial sections.

Using Golgi-stained serial sections obtained at the sacro-caudal levels of the cat spinal cord, it was possible to reconstruct the trajectory of primary afferents. They were classified into two groups: reliable primary afferents directly traced from the dorsal root and probable primary afferents traced from the dorsal funiculus or Lissauer's tract. The diameters of the reliable primary afferents vary from 0.88-1.88 mum. According to their courses, reliable primary afferents as well as probable primary afferents were classified into three groups: the first is distributed to both medial and lateral halves of the dorsal horn, the second to the medial half, and the third to the lateral half. Commissural fibers were also observed among the probable primary afferents. The rostro-caudal and medio-lateral extents of reliable primary afferents are found to be between 250 and 950 mum and 270 and 700 mum respectively, while those of the probable primary afferents were between 125 and 670 mum and 270 and 1,640 mum respectively. These primary afferent fibers are connected with at least two or more laminae of the dorsal horn gray matter.

Afferent Pathways↗

PubMed1985

Observations on the somatodendritic morphology and axonal trajectory of intracellularly HRP-labeled efferent neurons located in the deeper layers of the superior colliculus of the cat.

Efferent neurons of the deeper layers of the cat's superior colliculus were stained with horseradish peroxidase (HRP) to demonstrate patterns of somatodendritic morphology and axonal trajectory. A combination of somatodendritic and axonal features of the HRP-labeled cells revealed the existence of three major groups of tectal efferent neurons (X, T, and I). X neurons are mostly large and multipolar and participate in the crossed descending and ipsilateral ventral ascending projections of the superior colliculus. The X group includes multipolar radiating (X1), tufted (X2), large vertical (X3), medium-sized vertical (X4), and medium-sized horizontal (X5) neurons. T neurons participate in one or two of the major tectofugal bundles (medial descending ipsilateral, lateral descending ipsilateral, medial dorsal ascending, crossed descending) besides providing a commissural branch. They also issue recurrent collaterals distributed within a more or less restricted area of the deeper layers. The T group includes medium-sized, trapezoid, radiating (T1) and small or medium-sized, ovoid, vertical (T2) neurons. I neurons participate in the ipsilateral descending projection of the superior colliculus. They are small, triangular or ovoid, sparsely ramified cells that provide long, varicose collaterals irregularly distributed within the deeper layers. The majority of T neurons are located in the ventral stratum opticum or dorsal stratum griseum intermediale; X3 and X5 neurons are situated immediately below in the dorsal stratum griseum intermediale, while X1, X2, X4, and I neurons are indiscriminately distributed within the deeper layers. The polythetic classification presented here provides a conceptual framework for the description of tectal efferent neurons. It is open-ended and can thereby accommodate new cells types as indicated by the disclosure of a small horizontal (A) and a small radiating (unclassified) neuron. Moreover, it does not preclude the construction of alternate taxonomies. A dendro-architectonic classification into four groups [vertical (X3, X4, T2, I), horizontal (X5, A), radiating (X1, T1, I), and tufted (X2)] can be made and would relate to the mode of integration of various tectopetal inputs. A classification based on the dorsoventral location of tectal efferent neurons is also possible and would relate to the dorsoventral distribution of neurons with specific response properties.

Animals↗

PubMed1985

Funicular trajectories of brainstem neurons projecting to the lumbar spinal cord in the monkey (Macaca fascicularis): a retrograde labeling study.

Brainstem nuclei projecting to the lumbar spinal cord in the monkey were identified by using horseradish peroxidase and the fluorescent dye granular blue. These retrogradely transported tracers were used in fluid and/or gel forms to determine the funicular trajectories of the brainstem-spinal projections. The major descending components of the dorsal funiculus arose from the n. gracilis, n. cuneatus, and the n. of the solitary tract. Major components of the dorsolateral funiculus (DLF) came from the raphe complex, medullary and pontine reticular formation, locus coeruleus, Edinger-Westphal n., and red n. Other nuclei giving rise to minor contributions to the DLF included n. gracilis, n. cuneatus, n. of the solitary tract, medial and spinal vestibular n., subcoeruleus, periaqueductal gray, interstitial n. of Cajal, n. of Darkschewitsch, and the anteromedian n. The major components of ventral cord paths (ventrolateral and ventral funiculi) arose from the raphe complex, the medullary and pontine reticular formation, lateral and spinal vestibular n., and the coerulean complex. Minor contributions to the ventral paths descended from the dorsal motor n. of X, n. of the solitary tract, medial vestibular n., paralemniscal reticular formation, dorsal parabrachial n., n. cuneiformis, periaqueductal gray, Kölliker-Fuse n., and red n. The possible functional implications of the funicular distribution of these descending pathways are discussed from the perspective of descending inhibition and pain modulation.

Afferent Pathways↗

PubMed1988

Descending projections from the gigantocellular tegmental field in the cat: cells of origin and their brainstem and spinal cord trajectories.

The trajectories and the cells of origin of the pontobulbar gigantocellular tegmental field descending pathways were studied in the cat using anterograde WGA-HRP and retrograde HRP techniques. Four main descending pathways and cells of origin were delineated: (1) Predominantly large neurons in the pontine gigantocellular tegmental field (average soma diameter = 43.4 microns) and rostral bulbar gigantocellular tegmental field (41.3 microns) gave rise to reticulospinal fibers descending in the ipsilateral medial longitudinal fasciculus and ventral funiculus and distributed in laminae V-X with an ipsilateral predominance. These were primarily large-diameter fibers. (2) Predominantly large neurons (46.9 microns) in the bulbar gigantocellular tegmental field gave rise to reticulospinal fibers descending in the contralateral medial longitudinal fasciculus and ventral funiculus. These were mainly large-diameter fibers. (3) Neurons of predominantly medium size (29.5 microns) in the pontine gigantocellular tegmental field gave rise to reticuloreticular fibers descending directly to and distributed bilaterally in the bulbar reticular formation. These were small-diameter fibers. (4) Neurons of predominantly medium size (28.9 microns) in the bulbar gigantocellular tegmental field gave rise to reticulospinal fibers descending in the ipsilateral reticular formation and lateral funiculus. These were small-diameter fibers.

Animals↗

PubMed1989

Neurons of origin and fiber trajectory of amygdalofugal projections to the medial preoptic area in Syrian hamsters.

The amygdaloid neurons of origin and the trajectory of amygdaloid fibers to the medial preoptic area of the adult male Syrian hamster were identified by using horseradish peroxidase (HRP) histochemistry. After iontophoresis of HRP into the medial preoptic area, retrogradely labeled amygdaloid neurons were located in the dorsal and caudal parts of the medial amygdaloid nucleus and throughout the amygdalohippocampal area. No amygdaloid neurons were labeled after HRP applications confined to the most rostral portion of the medial preoptic area (anterior to the body of the anterior commissure). Following more caudal medial preoptic area injections (body of the anterior commissure to the suprachiasmatic nucleus) the distribution of retrogradely labeled cells in the medial amygdaloid nucleus and the amygdalohippocampal area revealed no topographic organization of the amygdalopreoptic connections. When amygdaloid neurons were labeled, the amygdalohippocampal area contained two to five times as many HRP-filled cells as the medial amygdaloid nucleus. Retrogradely transported HRP could be followed from the medial preoptic area to the amygdala through fibers in the dorsomedial quadrant of the stria terminalis. In addition, electrolytic lesions of the stria terminalis prior to iontophoresis of HRP into the medial preoptic area prevented retrograde transport to neurons in both the dorsocaudal medial amygdaloid nucleus and the amygdalohippocampal area. These results confirm earlier observations describing the location of autoradiographically labeled efferents from the medial amygdaloid nucleus to the medial preoptic area and provide new information about the restricted region within the medial amygdaloid nucleus from which these projections arise. They also suggest that, unlike the projections from the medial amygdaloid nucleus to the bed nucleus of the stria terminalis, the efferents to the medial preoptic area travel entirely in the stria terminalis.

Amygdala↗

PubMed1990

Demonstration of two separate descending noradrenergic pathways to the rat spinal cord: evidence for an intragriseal trajectory of locus coeruleus axons in the superficial layers of the dorsal horn.

The rat spinal cord receives noradrenergic (NA) projections from the locus coeruleus (LC) and the A5 and A7 groups. In contradiction to previous statements about the distribution of descending NA axons, we have recently proposed that in the rat LC neurons project primarily to the dorsal horn and intermediate zone, whereas A5 and A7 neurons project to somatic motoneurons and the intermediolateral cell column. The aim of the present study was to determine the funicular course and terminal distribution of descending NA axons from the LC and from the A5 and A7 groups. The organization of the coeruleospinal projection was analyzed by using the anterograde tracer Phaseolus vulgaris leucoagglutinin in combination with dopamine-beta-hydroxylase immunohistochemistry. The trajectory of A5 and A7 axons was studied in spinal cord sections of rats following ablation of the coeruleospinal projection with the neurotoxin DSP-4. To assess the relative contribution of the LC and the A5 and A7 groups to the NA innervation of the spinal cord, unilateral injections of the retrograde tracer True Blue were made at cervical, thoracic, and lumbar levels, and retrogradely labeled NA neurons were identified by dopamine-beta-hydroxylase immunofluorescence. The results of the anterograde tracing experiments confirm our previous findings that LC neurons project most heavily to the dorsal horn and intermediate zone. Analysis of horizontal sections revealed that LC axons descend the length of the spinal cord within layers I and II. In contrast to the intragriseal course of LC fibers, A5 and A7 axons travel in the ventral and dorsolateral funiculi and terminate in the ventral horn and the intermediolateral cell column. Retrograde transport studies indicate that the contribution of the A5 and A7 groups to the NA projection to the spinal cord is greater than that of the LC. We conclude that descending axons of the LC and A5 and A7 groups differ in their course and distribution within the spinal cord. The documentation of a definite topographic order in the bulbospinal NA projections suggests that the LC and the A5 and A7 groups have different functional capacities. The LC is in a position to influence the processing of sensory inputs, in particular nociceptive inputs, whereas A5 and A7 neurons are likely to influence motoneurons.

Animals↗

PubMed1992

Axonal trajectories and distribution of GABAergic spinal neurons in wildtype and mutant zebrafish lacking floor plate cells.

The role of the midline floor plate cells in the neuronal differentiation of the spinal cord was examined by comparing putative GABAergic neurons in wildtype zebrafish embryos with those in cyc-1 mutant embryos. The mutation produces a pleiotropic recessive lethal phenotype and is severe in rostral brain regions, but its direct effect in the caudal hindbrain and the spinal cord is apparently restricted to the depletion of the midline floor plate cells. In wildtype embryos, an antibody against the neurotransmitter GABA labeled the cell bodies, axons, and growth cones of three classes of previously identified neurons; dorsal longitudinal neurons (DoLA), commissural secondary ascending neurons (CoSA), and ventral longitudinal neurons (VeLD). A novel ventral cell type, Kolmer-Agduhr (KA) neurons, was also labeled. In the cyc-1 mutant, abnormalities were observed in some, but not all, of the GABAreactive CoSA, VeLD, and KA axons, while the axonal trajectories of DoLA neurons were not affected. Furthermore, the number of KA cells was reduced in the mutant while the numbers of the other GABAreactive cells were unperturbed. These observations corroborate our earlier hypothesis that the floor plate cells are one of several guidance cues that direct axonal outgrowth near the ventral midline of the spinal cord. They also suggest that the floor plate cells may play a role in the cellular differentiation of the spinal cord of zebrafish embryos.

Animals↗

PubMedDate not supplied

Recovery trajectory of unpartnered elders after myocardial infarction: an analysis of daily diaries.

The study reported here analyzed daily diary entries of unpartnered elders after myocardial infarction (MI) to gain perspective into their recovery. A total of 33 diaries were included as part of the qualitative analysis of the larger study referred to above. Diary content was evaluated through qualitative descriptive analysis. Six categories--activities of daily living, exercise practices, social support, symptom reporting, healthcare activities, and health-related expenses--were identified from the diaries. Results suggest that recovering, unpartnered MI elders have a need to return to a familiar lifestyle. Moreover, a few differences and similarities based on gender were found. In the rehabilitation setting, nurses should recognize the need for elders to return to normal activities, the importance of social support, the acknowledgement of gender differences, and the potential cost burden for these patients. Diaries were a valuable tool with which to uncover information about the recovery trajectory of unpartnered elders after MI.

Activities of Daily Living↗

PubMedDate not supplied

The prevention of disablement: A framework for the breast cancer trajectory.

More than 2 million women in the United States are breast cancer survivors. This is largely due to advances in early detection and treatment and is underscored by a survival rate of 88% at 5 years postdiagnosis for all stages of breast cancer. Although much progress has been made in combating the disease, women diagnosed with breast cancer endure multiple assaults to the body both from the disease and treatments. Surgical and adjuvant therapies are associated with complications and side effects that may lead to functional limitations, disability, and a poor quality of life. The Model of Disability and Disability Prevention provides a framework for addressing the challenges of the breast cancer trajectory. From pathology to disability, the model offers an approach to preventative and restorative interventions. Exercise is highlighted as an intervention that significantly affects the breast cancer experience at multiple points along the disablement continuum.

Activities of Daily Living↗

PubMed2004

Trajectory of development in adolescents and adults with autism.

This article seeks to elucidate the trajectory of development in adolescents and adults with autism. Prospective, retrospective, and cross-sectional studies are reviewed to reveal the manifestation of and changes in the core symptoms of autism in adolescence and adulthood. Comparing children with adolescents and adults, modest degrees of symptom abatement and improvement in skills have been documented in multiple studies, as are increases in verbal and decreases in performance IQ. Nevertheless, most individuals do not attain normative outcomes in adulthood and continue to manifest significant degrees of symptomatology and dependency. However, a small sub-group (about 15%) has more favorable adult outcomes.

Adolescent↗

PubMed2002

Time-resolved contrast-enhanced imaging with isotropic resolution and broad coverage using an undersampled 3D projection trajectory.

Time-resolved contrast-enhanced 3D MR angiography (MRA) methods have gained in popularity but are still limited by the tradeoff between spatial and temporal resolution. A method is presented that greatly reduces this tradeoff by employing undersampled 3D projection reconstruction trajectories. The variable density k-space sampling intrinsic to this sequence is combined with temporal k-space interpolation to provide time frames as short as 4 s. This time resolution reduces the need for exact contrast timing while also providing dynamic information. Spatial resolution is determined primarily by the projection readout resolution and is thus isotropic across the FOV, which is also isotropic. Although undersampling the outer regions of k-space introduces aliased energy into the image, which may compromise resolution, this is not a limiting factor in high-contrast applications such as MRA. Results from phantom and volunteer studies are presented demonstrating isotropic resolution, broad coverage with an isotropic field of view (FOV), minimal projection reconstruction artifacts, and temporal information. In one application, a single breath-hold exam covering the entire pulmonary vasculature generates high-resolution, isotropic imaging volumes depicting the bolus passage.

Abdomen↗

PubMed1991

Image reconstruction from Fourier domain data sampled along a zig-zag trajectory.

When the conventional Fourier transform (FT) algorithm is applied to reconstruct a magnetic resonance (MR) image from data sampled along a zig-zag trajectory in the Fourier space, the nonuniform sampling in the spatial frequency direction may give rise to artifacts. In this paper the nature of the artifacts is analyzed and an alternative reconstruction algorithm is developed to produce artifact-free images. Methods for reducing noise level in the reconstructed image are discussed. Our approach is compared with another method based on the interlace sampling theorem.

Algorithms↗

PubMed1995

Compensation of multi-dimensional selective excitation pulses using measured k-space trajectories.

Multidimensional spatially selective excitation pulses rely on the accuracy of gradient waveforms to achieve desired excitation volumes. Unfortunately, the high gradient slew-rates and magnitudes required by these pulses often lead to distortion of the waveforms produced by imaging systems resulting in poor selection profiles. In this paper, a k-space calibration procedure, used to determine the actual trajectory produced by the scanner's field gradients, is extended to two spatial dimensions. This measured information is then incorporated in a selective excitation design technique for correcting the RF pulse envelopes to compensate for gradient waveform induced distortion of the excitation volumes.

Magnetic Resonance Imaging↗