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PubMed1984

Control of axonal caliber by neurofilament transport.

The role of neurofilaments, the intermediate filaments of nerve cells, has been conjectural. Previous morphological studies have suggested a close relationship between neurofilament content and axonal caliber. In this study, the regenerating neuron was used as a model system for testing the hypotheses that neurofilaments are intrinsic determinants of axonal caliber, and that neurofilament content is controlled by the axonal transport of neurofilaments. This system was chosen because previous studies had shown that, after axotomy, axonal caliber was reduced within the proximal stump of the regenerating nerve and, because the relative amount of neurofilament protein undergoing axonal transport in regenerating axons was selectively reduced. The relationship between axonal caliber and neurofilament number was examined in a systematic fashion in both regenerating and control motor axons in rat L5 ventral root. Reconstruction of the spatial and temporal sequences of axonal atrophy in the proximal stump after axotomy showed that reductions in axonal caliber were first detected in the most proximal region of the root and subsequently progressed in a proximal-to-distal direction at a rate of 1.7 mm/day, which is identical to the rate of neurofilament transport in these neurons. Quantitative ultrastructural studies showed that these reductions in caliber correlated with a proportional decrease in the number of axonal neurofilaments but not microtubules. These results support the hypotheses that neurofilament content is a major intrinsic determinant of axonal caliber and that neurofilament content is controlled by the axonal transport of neurofilaments. On this basis, we suggest a role for neurofilaments in the control of axonal volume.

Animals↗

PubMedDate not supplied

Temporal correlation images derived from sequential MR scans.

In this paper a new technique is presented for measuring the local temporal changes and correlation between them on spatially aligned image sequences. A temporal correlation image is derived from a sequence of static images (frames). The method is illustrated in an application to the dynamic MRI of the rabbit kidney following bolus injection of Gd-DTPA. The similarity maps clearly separate the dynamic response of the cortex to the indicator from that of the medulla and, therefore, segment the kidney into two regions. Regions with different temporal dynamics can be displayed in different colors using a lookup table designed for that purpose.

Animals↗

PubMed1988

Cellular pattern of photosynthetic gene expression in developing maize leaves.

Leaf development in C4 plants such as maize involves the differentiation of two photosynthetic cell types [bundle sheath (BS) and mesophyll (M)] to form Kranz-type leaf anatomy. This cellular dimorphism partitions photosynthetic activities so that each enzyme of the C4 pathway accumulates only in the appropriate cell type. We have exploited this property to study BS and M cell interactions in developing maize leaves. Our previous studies showed that C4 proteins appear concurrently with the appearance of Kranz anatomy. To look at earlier events in BS and M cell development we have used three of the corresponding C4 mRNAs as cell-specific markers. We have followed, in situ, the accumulation of malic enzyme (ME), phosphoenolpyruvate carboxylase (PEPCase), and ribulose bisphosphate carboxylase (RuBPCase) mRNAs in developing leaves of both normal and mutant argentia (ar) maize. We have isolated a partial cDNA clone for maize ME to examine ME mRNA expression. We show that throughout the development of light-grown seedlings, all three mRNAs accumulate in a cell-specific fashion in both normal and ar leaves. The pattern of C4 mRNA accumulation longitudinally along the veins, laterally across the leaf, and locally around individual veins reveals the spatial and temporal sequence of BS and M cell development. BS cell-specific mRNAs accumulate around developing veins before Kranz anatomy is evident morphologically. Our analysis of the ar mutant, in which C4 mRNA appearance is delayed relative to the appearance of Kranz anatomy, demonstrates first that BS and M cells develop in clusters across the leaf blade and second that BS cells surrounding any individual vein are activated asynchronously. We discuss our results in relation to models and mechanisms of BS and M cell development.

Cell Compartmentation↗

PubMed2003

RNAi microarray analysis in cultured mammalian cells.

RNA interference (RNAi) mediated by small interfering RNAs (siRNAs) is a powerful new tool for analyzing gene knockdown phenotypes in living mammalian cells. To facilitate large-scale, high-throughput functional genomics studies using RNAi, we have developed a microarray-based technology for highly parallel analysis. Specifically, siRNAs in a transfection matrix were first arrayed on glass slides, overlaid with a monolayer of adherent cells, incubated to allow reverse transfection, and assessed for the effects of gene silencing by digital image analysis at a single cell level. Validation experiments with HeLa cells stably expressing GFP showed spatially confined, sequence-specific, time- and dose-dependent inhibition of green fluorescence for those cells growing directly on microspots containing siRNA targeting the GFP sequence. Microarray-based siRNA transfections analyzed with a custom-made quantitative image analysis system produced results that were identical to those from traditional well-based transfection, quantified by flow cytometry. Finally, to integrate experimental details, image analysis, data display, and data archiving, we developed a prototype information management system for high-throughput cell-based analyses. In summary, this RNAi microarray platform, together with ongoing efforts to develop large-scale human siRNA libraries, should facilitate genomic-scale cell-based analyses of gene function.

Cell Line, Tumor↗

PubMed1989

The ventricular depolarization gradient: effects of exercise, pacing rate, epinephrine, and intrinsic heart rate control on the right ventricular evoked response.

A new pacing technique is described that permits high fidelity recording of the paced ventricular evoked response, including cardiac depolarization. Integration of the paced R wave yields the ventricular depolarization gradient (GD), which is dependent on activation sequence and the spatial dispersion of activation times. GD was studied in 27 dogs to determine the effects of treadmill exercise at fixed rate pacing (n = 10), elevation of heart rate in the absence of stress (n = 20), epinephrine at fixed rate (n = 6), and exercise in the presence of normal chronotrophic response (n = 7). Low level exercise (1 mph, 2 min, 15 degrees) at a fixed heart rate produced significant (P less than 0.0005) decreases in GD that averaged -10.8 +/- 4.0% (mean +/- SD). The rate of change in GD was faster at the onset of exercise than at its cessation (P less than 0.0005). Artificial elevation of heart rate at rest produced significant (P less than 0.0005) increases in GD; mean sensitivity of GD to rate was 0.27 +/- 0.12%/beats/min. Intravenous injection of epinephrine produced significant (P less than 0.001) decreases in GD at two dosage levels (2.5 and 5.0 micrograms/kg) when evaluated at two baseline pacing rates (150 and 190 beats/min); mean changes in GD were -20.64 +/- 0.53% (2.5 micrograms/kg at 150 beats/min), -25.19 +/- 4.20% (5.0 micrograms/kg at 150 beats/min), -14.18 +/- 5.19% (2.5 micrograms/kg at 190 beats/min), and -24.22 +/- 4.94% (5.0 micrograms/kg at 190 beats/min). Sensitivity of GD to epinephrine was dose-dependent (P less than 0.01) at each baseline rate, but was independent (P greater than 0.05) of the rate itself. In the presence of a normal chronotropic response, GD remained unchanged (P greater than 0.5) during exercise in spite of significant elevation in heart rate (105.0 to 167.1 beats/min, P less than 0.001). These data suggest the presence of an intrinsic negative-feedback control mechanism that maintains GD constant in the healthy heart during homeostatic disturbance. Applications in closed-loop rate adaptive pacing are described.

Animals↗

PubMed1992

Interaction of Epstein-Barr virus nuclear antigen 1 with the viral latent origin of replication.

The Epstein-Barr virus latent origin of replication (oriP) requires only one viral protein, the Epstein-Barr virus nuclear antigen 1 (EBNA-1), for activity. oriP consists of two spatially separated, essential sequence elements, regions I and II, both of which contain multiple EBNA-1-binding sites. Region II contains, or is close to, the site at which DNA synthesis initiates. The role of region I, a transcriptional enhancer in cells that express EBNA-1, in replication is not understood. To determine how the binding of EBNA-1 to sites in region II leads to the initiation of DNA synthesis and to investigate the role of region I, EBNA-1 has been overproduced in insect cells by using a baculovirus vector and purified to homogeneity, and the interaction of EBNA-1 with oriP has been examined. Footprinting experiments demonstrated that EBNA-1 binds to oriP in a sequence-specific manner and bends or untwists the DNA at two symmetry-related sites in region II. Distortion of region I by EBNA-1 was not detected, suggesting that differences in the spacing of binding sites in regions I and II and resulting protein-protein interactions underlie differences in their biological properties. KMnO4 footprinting experiments did not reveal significant single-stranded structures in region II, suggesting that cellular proteins may recognize the EBNA--region II complex and unwind the DNA duplex. Region I did not quantitatively or qualitatively alter the interaction of EBNA-1 with region II. The contribution of an A + T-rich sequence in region II to replication was investigated by a mutational analysis. The results indicated that the overall A + T-rich nature of this sequence is not essential for replication of oriP-bearing plasmids. Nuclease protection experiments performed with these mutagenized plasmids provided additional evidence for protein-protein interactions in region II.

Animals↗

PubMed1991

Phase-dependent modulations of anticipatory postural activity during human locomotion.

1. The ability of the CNS to coordinate several motor tasks was studied in humans walking on a treadmill while pulling on a handle. Subjects were instructed to respond to an audio signal that was presented in different phases of the step cycle. Electromyograph (EMG) and movements were recorded from the left arm and leg. 2. The activity of the arm muscle was preceded by postural activity in the leg muscles. The pattern of the anticipatory postural activity differed in the various phases of the step cycle. Lateral gastrocnemius and hamstring muscles were activated during responses occurring in the early support phase whereas tibialis anterior and quadriceps muscles were activated when the pull was exerted during the late support phase and during the swing phase. In the middle of the support phase the combination of both muscle activity was present. 3. The temporal sequencing and the spatial distribution of the anticipatory muscle activity changed gradually. Early during the support phase the hamstring muscles were activated before the gastrocnemius muscle, whereas the order was reversed during midstance. The EMG amplitude of the hamstring and gastrocnemius muscles was largest in the beginning of the support phase and then gradually decreased, whereas the amplitude of the tibialis anterior and quadriceps muscles increased during the later parts of the support phase. 4. The anticipatory responses to pulls exerted during the first part of the support phase reduced the ankle flexion during the single support phase.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗

PubMed1998

Changes in GABAB modulation during a theta cycle may be analogous to the fall of temperature during annealing.

Changes in GABA modulation may underlie experimentally observed changes in the strength of synaptic transmission at different phases of the theta rhythm (Wyble, Linster, & Hasselmo, 1997). Analysis demonstrates that these changes improve sequence disambiguation by a neural network model of CA3. We show that in the framework of Hopfield and Tank (1985), changes in GABA suppression correspond to changes in the effective temperature and the relative energy of data terms and constraints of an analog network. These results suggest that phasic changes in the activity of inhibitory interneurons during a theta cycle may produce dynamics that resemble annealing. These dynamics may underlie a role for the theta cycle in improving sequence retrieval for spatial navigation.

Animals↗

PubMed2006

FLAIR-/T1-/T2-co-registration for image-guided diagnostic and resective epilepsy surgery.

OBJECTIVE: For technical reasons, T2-weighted and fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI) sequences do not allow morphological orientation with high anatomic resolution, but they may show small epileptogenic lesions. Considering the peculiarities of diagnostic and resective epilepsy surgery the present study focused on the co-registration of various magnetic resonance sequences for guided epilepsy surgery. METHODS: Fifty patients (24 men; 26 women) aged 2 to 74 years (mean, 32 yr), in whom epileptogenic lesions were not readily identifiable on three-dimensional T1-weighted MRI scans underwent additional two-dimensional T2-weighted and FLAIR sequences before diagnostic and/or resective epilepsy surgery. FLAIR and/or T2-weighted images were co-registered to the T1-weighted data set and were displayed on the navigation station on site for guided invasive diagnostics and for resection according to an individualized resection plan. Postoperative MRI scanning was routinely performed for assessment of resection extent. RESULTS: Co-registered T1- and FLAIR-/T2-images allowed for image-guided intraoperative identification of all lesions (n = 50). Control MRI scans revealed that complete resection was performed as planned before the operation in 49 patients and incomplete resection was performed in one patient. Preliminary seizure outcome with a mean follow up of 14 months (range, 7-24 mo) was assigned according to the Engel classification: Class I, 78%; Class II, 12%; Class III, 4%; Class IV, 6%. CONCLUSION: Image guidance on the basis of image fusion/co-registration of T1- and FLAIR-/T2-images allows for intraoperative identification of otherwise poorly visible lesions on standard MRI sequences in good spatial resolution. Recall of this information during surgery from the navigation system's screen assists in achieving the goal of precise electrode placement, or complete resection of the lesion as well as of the perilesional epileptogenic tissue and improves the surgeon's intraoperative orientation.

Adolescent↗

PubMed2002

Optical high-precision three-dimensional vision-based quality control of manufactured parts by use of synthetic images and knowledge for image-data evaluation and interpretation.

Vision-based evaluation of industrial workpieces can make efficient use of knowledge-based approaches, in particular for quality control, inspection, and accurate-measurement tasks. A possible approach is to compare real images with conceptual (synthetic) images generated by use of standard computer-aided design models, which include tolerances and take the application-specific conditions into account (e.g., the measured-calibration data). Integrated in (industrial) real-life environments, our evaluation methods have been successfully applied to on-line inspection of manufactured parts including sculptured surfaces, using structured light techniques for the reconstruction of three-dimensional shapes. Accuracies in the range 15-50 microm are routinely achieved by use of either isolated images or spatially registered image sequences.

Journal Article↗

PubMed2005

A fast high-resolution multislice T1-weighted turbo spin-echo (TSE) sequence with a DRIVen equilibrium (DRIVE) pulse for native arthrographic contrast.

OBJECTIVE: This article describes a simple method to produce native arthrographic contrast in a fast T1-like turbo spin-echo sequence with the use of a driven equilibrium pulse. CONCLUSION: Our 2D multislice turbo spin-echo sequence combined with a driven equilibrium pulse provides a bright signal of joint fluid with otherwise unchanged signal intensities as compared with a normal T1-weighted turbo spin-echo sequence at high spatial resolution and short scan times. Thus, it might represent a useful adjunct for routine joint examinations.

Adult↗

PubMed2000

WISC-III subtest patterns of ADHD and normal samples.

WISC-III subtest patterns of children with Attention Deficit Hyperactivity Disorder were compared with two other groups of children described in the WISC-III manual, a sample with Attention Deficit Hyperactivity Disorder and the WISC-III standardization sample. Subtest patterns of primary interest were the SCAD Index based on Symbol Search, Coding, Arithmetic, Digit Span, Bannatyne scores for Spatial, Verbal Conceptualization, Sequencing Ability, and the ACID Profile including Arithmetic, Coding, Information, and Digit Span. Comparisons of WISC-III scaled scores and subtest patterns for the samples with Attention Deficit Hyperactivity Disorder supported the congruence between them. Further, the cumulative percentages of children in the three samples who obtained differences between the SCAD Index and the Perceptual Organization Index were computed. Analysis indicated that 17 of the 35 subjects in the current sample obtained differences of 9 points or greater. The results were substantially different from the WISC-III standardization sample but congruent with the WISC-III sample of children with Attention Deficit Hyperactivity Disorder. These outcomes support the diagnostic utility of WISC-III subtest profile patterns for children with Attention Deficit Hyperactivity Disorder.

Adolescent↗

PubMed1996

Localisation of hepatocyte growth factor and its receptor (c-met) protein and mRNA in human term placenta.

Successful pregnancy depends upon placental growth and development, which follows a specific spatial and temporal sequence. Hepatocyte Growth Factor (HGF) is a potent mitogen, morphogen and motogen to both endothelial and epithelial cell types and is linked to a tyrosine kinase, proto-oncogene, c-met receptor. In 'normal' third trimester placentae (n = 5) full thickness biopsies (obtained at Caesarean section), immunolocalisation and in situ hybridisation studies were performed for HGF and c-met., respectively. HGF immunoreactive protein was present in mesenchymal core, the vaculosyncytial membrane (syncytotrophoblast) and the vascular endothelial cells of villous trophoblast. The HGF mRNA was present particularly strongly in the perivascular stromal cells surrounding the villous vasculature and the amnion/chorionic membranes. Immunoreactive c-met protein was strongly localised to the endothelial cells lining the villous vasculature and the vasculosyncytial membrane. A relatively weak and diffuse hybridisation signal for c-met mRNA was present throughout the villous trophoblast, most pronounced in the vasculosyncytial membrane. These results indicate that HGF may serve as a paracrine mediator to control placental development and growth.

DNA Probes↗

PubMedDate not supplied

[Cognitive disorders in patients with Huntington's disease].

INTRODUCTION: Huntington s disease has been clearly recognized since 1872. It is characterized by the appearance of a motor disorder (chorea) accompanied by selective cognitive deterioration which is not interfered with by aging. DEVELOPMENT: Since the genetic defect causing it has been identified (expansion of CAG triplets on the IT 15 gene of chromosome 4) it has been possible to study families from the preclinical stage (asymptomatic persons who carried the mutation) to the stage of full development of the clinical syndrome. The behaviour disorders most often seen in these patients are depression, mania, schizophrenia, paranoia, anxiety, obsessive and obsessive compulsive disorders although other disorders may also occur. Different clinical forms of motor disorders and dementia have been reported in relation to the age of onset of the symptoms. The commonest cognitive symptoms are defects of attention, memory, planning, sequencing and visuo spatial deficits, as occurs in subcortical dementia. Our objective is to present the different clinical forms of the disorder according to the age of presentation, implication of the symptoms, severity of the genetic defect (number of CAG triplets) and to describe the study made of asymptomatic carriers so as to be able to detect incipient cognitive deterioration in these persons.

Adolescent↗

PubMedDate not supplied

[The problem of archetype and current biology].

Two ideas of homology--transformational and taxic--are used in biology. The first one deals with homology of different structures from morphological point of view, the second one--with the homology of characters. The main question of taxic homology is: in what cases the same character is not identical in two different species? Transformational homologies are determined according the archaetype, taxic ones--according inheritance from the common ancestor of comparing taxa. Archaetype is an idea of an organism from the position of its components. Archaetype should be distinguished from the type character, i.e. the description of an organism combining general and special features. The main idea of archaetype is an idea of coherence of characters describing morphological organization. Archaetype was considered by Owen as mechanical construction. As a matter of fact, the organism is a dynamic system Its dynamic nature can be demonstrated by the conception of module organization of living systems. In the framework of this conception archaetype is a description of an organism from constructive position, focused on the characters of the parts reflecting ontogenetic and evolutionary autonomy. The progress in developmental genetics in understanding of genetic mechanisms of spatial structure formation during the last years opens the wide perspectives in interpretation of archaetype idea. Homeobox family of genes of Hox complex is especially interesting from this point of view. They are characterized by colinearity: spatial and temporal sequence of their expression is corresponding to their order in chromosome. As it was shown by several experiments, changes in the level and sequence of expression of Hox genes result in the changes of archaetype. The discovery of homological genes determining non homological morphological structures in non related groups is a new challenge to morphologists studying the problem of homologies. The disagreements on this subject are connected with non critical use of transformational (archaetypical) and taxic approximations. From transformational positions, eyes of vertebrates and invertebrates are homological, although they have different structure. At the same time, if we specify what type of eyes we are considered, the results will change. Thus, compound eyes of insects and bivalve mollusk Arca are not homological because they originated independently from forms without compound eyes.

Animal Population Groups↗

PubMed2004

[Conservation priorities for plant species of forest-meadow ecotone in Sanjiangyuan Nature Reserve].

Based on field survey, information collection and experts consultation, the quantitative grading index system and assessment standards for preference conservation of rare and endangered plant species of forest-meadow ecotone in Sanjiangyuan Nature Reserve were established by using the methods and principles of systematical analysis. The quantitative grading index system included endangered coefficient, genetic coefficient, and useful value coefficient. In addition, 10 indicators used to evaluate endangered grading and conservation priorities sequenc, were also included in 3 subsystems respectively. Furthermore, the weights of 3 subsystem and 10 indicators were given through experts consultation and analytic hierarchy process. Endangered coefficient and conservation priorities coefficient, which respectively described the endangered grading, and preferential conservation of plant species were calculated by mathematic models and computer program. Contrasting to the standards of endangered grading and conservation priorities for plant species, we quantitatively evaluated the status of endangered and conservation priorities of plant species. The results showed that the number of endangered species was 4, vulnerable species 68, lower risk species 179, safety species 695; the number of the first class species was 8, the second class species 78, the third class species 164, and the delayed conservation species 696. Finally, we discussed the problems of indicator system and its weight, the relationship between endangered grading and conservation priorities sequence, and the spatial scale problem of plant species assessment.

Biodiversity↗

PubMed2005

Experimental autoimmune encephalomyelitis in the rat spinal cord: lesion detection with high-resolution MR microscopy at 17.6 T.

BACKGROUND AND PURPOSE: Experimental autoimmune encephalomyelitis (EAE) is an inflammatory demyelinating disorder of the CNS and an animal model of multiple sclerosis. We used high-field MR microscopy at 17.6 T to image spinal cord inflammatory lesions in the acute stage of chronic relapsing rat EAE. We sought to compare lesions detected on MR imaging with histopathologic findings and to quantify the inflammatory lesion load. METHODS: Imaging of fixed spinal cord specimens was performed by using a 3D gradient-echo sequence with a spatial resolution of 35 x 35 x 58 microm3 and a total imaging time of 5.5 hours. Histopathologic analysis was performed by staining axial sections with hematoxylin-eosin or Luxol fast blue to identify cellular infiltration and demyelination. RESULTS: Clinical signs of EAE occurred on days 10-14 after immunization. On day 22, healthy white matter and gray matter were differentiated by high contrast on T2*-weighted images, with white matter lesions appearing as hyperintense areas in the normal-appearing white matter. Inflammatory lesions identified on histopathologic evaluation were readily detected with MR imaging and vice versa. MR imaging and histopathologic analysis had excellent correlation regarding the extent of white matter lesions. Inflammatory infiltrates of gray matter were not detectable with MR imaging. Using a semiautomatic segmentation of the acquired MR data, we could quantify white matter lesion load. CONCLUSION: Ex vivo high-resolution MR microscopy of the spinal cord at 17.6 T allows rapid and highly accurate determination of CNS inflammation by demonstrating virtually all histologically detectable white matter inflammatory lesions.

Animals↗

PubMed2004

ICA methods for MEG imaging.

Activity of individual cortical sources cannot be uniquely imaged when MEG data is a sequence of complex spatial patterns of multiple cortical sources. Auxiliary constraints integrated into the imaging equations are required to remove the mathematical ambiguity. Therefore, it is important to adapt source separation techniques to MEG imaging. It is much easier to accurately image field patterns of isolated brain electric sources. We demonstrate how a combination of second and fourth order Independent Component Analysis (ICA) methods can be used to remove noise and isolate source activity for improved MEG imaging accuracy. A second order ICA technique was used to extract respiratory and eye movement artifact by exploiting cross-correlation differences over time between cortical sources and artifact. For brain electric source separation, a fourth order ICA technique that quantified probabilities of simultaneous source activity was used to separate brain electric sources characterized by bursts of oscillatory circuit activity.

Humans↗