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PubMed1988

Positron emission tomography: clinical status in the United States in 1987. ACNP/SNM Task Force on Clinical PET.

PET studies are now being used to provide unique clinical information in several conditions. PET is an accurate, noninvasive method of identifying patients with coronary artery disease. Furthermore, PET studies can accurately differentiate patients who will or will not benefit from revascularization procedures. In patients with partial epilepsy being considered for surgery, PET studies provide spatial localization of the focus that complements other tests in improving the surgical management of these patients. PET studies give important diagnostic and prognostic information in the management of patients with gliomas and can direct recurrence of tumor and distinguish it from radiation necrosis. These uses of PET are well documented, and their utility has been independently confirmed in several institutions. Several other areas of research are being pursued with PET, and these will probably develop into clinically useful procedures in the future.

Brain Neoplasms↗

PubMed1988

Fundamental physics of magnetic resonance imaging.

Although similar to computerized tomography, in that cross-sectional images are produced, the physical principles underlying magnetic resonance are entirely different. The MRI process, as commonly implemented, involves the excitation of hydrogen nuclei and the analysis of how these nuclei recover to the original equilibrium steady states that they had prior to excitation. This article discusses that process, that is, preparatory alignment, RF excitation, relaxation and signal measurement, and spatial localization.

Fourier Analysis↗

PubMed1986

Magnetic resonance spectroscopy of the musculoskeletal system.

Magnetic resonance spectroscopy can be used to characterize the bioenergetic state of the musculoskeletal system, and several marker compounds related to the tissue's biochemistry have been found to exist. Potential new techniques involving better spatial localization, spectral editing, and examination of nuclei other than phosphorus are in the developmental stage. Their development over the next few years will determine the extent to which MRS will become a universally used medical tool. However, the results with 31P alone guarantee a continued role in the study of muscular disease, peripheral vascular disease, and hypoxia and ischemia of the neonatal brain.

Adolescent↗

PubMed1987

[Inhibitory components in responses of neurons of the lateral suprasylvian area of the cat cortex].

Inhibitory components of neuronal responses to moving visual stimuli in the lateral suprasylvian area of the cat cortex have been studied. Comparison of PST histograms of responses to two opposite directions of the movement allows revealing changes in the spatial localization of discharge centres in receptive fields relative to the movement direction. In all neurons investigated which revealed monotonous stationary structure of receptive fields no subregions coincidental with the inhibitory components of the responses are found. The presented experiments have promoted a conclusion that inhibitory components of responses of observed neurons could represent aftereffects following excitation of the cell when the stimulus is crossing the discharge centre of the receptive field.

Animals↗

PubMedDate not supplied

[The role of inhibition processes in the development of functional properties of neurons of the vibrissa projection area in the cat somatosensory cortex].

The paper deals with the contribution of intracortical inhibitory processes to the organization of receptive fields in the vibrissae projection area of the somatosensory cortex. Inhibition blockade by means of microelectrophoretic application of picrotoxin and bicucullin was shown to lead to a loss of directional sensitivity of neurones. Activation of inhibition at remote glutamate application led to opposite changes: the neurones became directionally sensitive, and dependence was found between the spatial localization of activated neurones and the character of changes of detector parameters. Inhibitory processes caused by natural afferent stimulation led to similar changes of functional characteristics of neurones.

Afferent Pathways↗

PubMedDate not supplied

[Temporal organization of interneuronal relations in the cerebral cortex of the cat in relation to the level of alimentary motivation].

By means of records of multicellular activity, interneuronal relations and their modifications in two cortical zones (Visual and motor) were studied in cats at different levels of alimentary motivation. For quantitative evaluation of interneuronal relations the statistic method of cross-correlation analysis of impulse trains was used in determining the probability of the appearance of the discharge of one neurone after the impulse of the other one. For groups of neurones in both investigated cortical areas, three-neurones microsystems were singled out and their activity was analyzed by temporal parameters of interaction between neurones at the interval of 120 ms, both within one microarea (intraanalyzer connections) and between microareas of two cortical zones. The correlation of temporal parameters of interneuronal connections (temporal delays in the activity of neuronal pairs) changed depending on spatial localization of neurones and functional condition of the animals. The existence is suggested of "informational" (1-30 ms) and "motivational" (90-120 ms) values of interneuronal relations for interanalyser connections.

Animals↗

PubMedDate not supplied

[Osteoid osteoma and osteoblastoma of the vertebrae].

Five cases of osteoid osteoma and five cases of osteoblastoma of the spine are reported. All the patients underwent surgery and the radiographic diagnosis was always histologically confirmed. Conventional radiographic technique using tomography constantly permitted the diagnosis. Computed tomography was primarily useful for spatial localization of the lesion. The authors evaluate the radiographic findings of the two lesions discussing the symptoms which are suspected for these pathologic conditions. Bone scintigraphy must precede radiological examination.

Humans↗

PubMed1979

Response versus place learning by human infants.

Two cross-setional studies examined how infants learn the location of visual events. In Experiment 1, infants of 4, 8, and 12 mo of age learned to turn one way to view a novel pattern. In a subsequent transfer task, they were rotated to face the opposite side of the room. The 4-mo-old infants tended to err by repeating their previously learned response, but within 16-20 trials their performance was comparable to the higher levels maintained by the older infants. These results suggest that young infants learn the location of the pattern primarily in terms of response cues, whereas older infants employ both response cues and place cues. Experiment 2 was designed to independently assess the use of response cues and place cues by infants of 4, 8, 12, and 16 mo of age. All infants were able to rapidly learn and remember the location of the novel pattern when they were given response cues. There was a gradual emergence of place-cue use associated with age. It is suggested that the decrease in infant egocentricity in such spatial localization tasks may in fact reflect an age-related increase in the variety of reliable cues responded to by infants.

Cues↗

PubMed1984

Multinuclear NMR studies of naturally occurring nuclei.

The ability to obtain nuclear magnetic resonance spectra from spatially localized regions of living animals and patients has led to the possibility of measuring biochemical processes in vivo. Localization is generally achieved through the use of surface coils. Using this technique, intracellular pH, and concentrations of high-energy phosphates and "abnormal" marker compounds have been measured in animal organs (both in vitro and in vivo) and in human brain and muscle (in vivo). The majority of studies have used the P-31 nucleus, but carbon (C-13) and hydrogen (H-1) have also been studied. However, both C-13 and H-1 experiments have technical difficulties. Carbon-13 has a low natural abundance, and H-1-containing metabolites may have their signals obscured by the large water peak. The phosphorus studies have been largely preclinical, but diagnostic possibilities are appearing from the many research problems now under investigation.

Animals↗

PubMed1978

[Psychological features of treated phenylketonuric patients of preschool age].

Psychological features of 6 children with phenylketonuria were studied. The children were of 5--7 years of age and received special dietetic management. Regular studies of the "learning type" were used as a method of dynamic psychological examination. Despite the fact that the children were of different age and intellectual level, showing different behavior pattern and individual personality traits, all of them had some mental features in common. These features included peculiarities of the emotional-evolutional sphere, disturbed attention and working capacity, local spatial disorders and a weakly developed internal plan of action. These mental traits should be taken into consideration during pedagogical correction of defects in treated phenulketonuric children.

Attention↗

PubMed1981

[Uncommon locations of celomic cysts: a possible cause of error in mediastinal radiology (author's transl)].

Five cases of uncommon locations of mediastinal celomic cysts are presented. All cases were surgically proved. The importance of these locations in the differential diagnosis of mediastinal masses is stressed. The evaluation of their inner structure by computerized tomography is, without doubt, the best progress in radiological diagnosis of the mediastinum. This method allows, atraumatically, to confirm or exclude the cystic nature of the lesion in one with its precise spatial localization.

Adult↗

PubMed1994

Vaccination of sheep against Fasciola hepatica with glutathione S-transferase. Identification and mapping of antibody epitopes on a three-dimensional model of the antigen.

The glutathione S-transferases (FhGST) of the liver fluke Fasciola hepatica have been identified as novel vaccine candidates that protect sheep against a fluke infection. With the use of overlapping peptides covering the predicted amino acid sequences of four FhGST cDNAs, we have defined the linear epitopes recognized by polyclonal antibody from sheep vaccinated with FhGST. Dominant and minor epitopes were found to be present on all four of the sequences although some epitopes were shown to be specific to particular FhGST. A high percentage of the FhGST peptides were found to be antigenic although considerable variability in response to the peptides was observed among the animals. This analysis was extended to the IgG1 and IgG2 response at the peptide level. Based on the recently solved crystal structure of the rat mu-class GST 3-3, a three-dimensional model of one of the FhGST sequences was generated that allowed the predicted spatial localization of defined epitopes. Most epitopes were localized on regions of high flexibility and accessibility. A comparison of epitopes on FhGST with the B cell epitopes on Sm28, a 28-kDa GST from Schistosoma mansoni, has found few similarities. There was no correlation between an antibody response to linear peptide epitopes and the level of protection induced in sheep by vaccination with FhGST.

Amino Acid Sequence↗

PubMed1995

Animal models of emmetropization: matching axial length to the focal plane.

BACKGROUND: It has long been recognized that more people are emmetropic than would be expected from a random combination of the refractive and axial components of the eye. However, it has been difficult to determine whether this is the result of an active emmetropization mechanism. METHODS: This paper reviews some of the studies in animals that have been conducted during the past 20 years. Four basic paradigms have been used to determine whether the visual environment helps guide eyes to emmetropia: 1) observing the normal pattern of ocular development, 2) shifting the location of the focal plane with minus- (and plus-) power lenses, 3) removing focused images by visual form deprivation and, 4) restoring form vision after a period of visual deprivation. RESULTS: Data from many studies suggest that an active emmetropization mechanism guides the postnatal development of the eye, matching the axial length to the focal plane. In normal development, the axial length initially is generally short so that the photoreceptors are in front of the focal plane of the unaccommodated eye. The subsequent axial elongation eventually moves the photoreceptors to, but not past, the focal plane. When animals are raised with the focal plane shifted posteriorly with minus-power lenses, the eyes elongate to approximately match the displaced focal plane. When information about the location of the focal plane is removed by visual deprivation, the eyes elongate past the point of emmetropia and become myopic. When developing eyes that have become myopic from a brief period of form deprivation are re-exposed to patterned images, they can slow their axial elongation, gradually eliminating the myopia. Data from several species suggest that the axial length is regulated within the eye itself, involving direct, spatially local communication from the retina to the sclera. It also appears that the regulation of axial elongation involves active control of the scleral extracellular matrix. CONCLUSIONS: If humans have a similar mechanism, then successful emmetropization in children may involve two components. One is to inherit a fully functional emmetropization mechanism. Equally important is exposure to a "normal" visual environment. Deficiencies in either, or an interaction between a compromised mechanism and a non-optimal visual environment might also prevent emmetropization.

Accommodation, Ocular↗

PubMed1995

Requirement of the ETS domain transcription factor D-ELG for egg chamber patterning and development during Drosophila oogenesis.

The D-elg gene encodes an ETS domain transcription factor that functions in Drosophila oogenesis. D-elg belongs to a small group of genes that are required for the formation of both the anteroposterior and dorsoventral axes of the egg chamber. During oogenesis in D-elg mutant females, the spatial localization of oskar and gurken mRNAs in the oocyte is disrupted and a follicle cell enhancer trap marker identifies dorsoventral polarity defects. Also, specialized follicle cells, called border cells, fail to migrate from their anterior location to a position adjacent to the developing oocyte. Consistent with these phenotypes, D-elg shows genetic interactions with two genes required for normal egg chamber differentiation.

Animals↗

PubMed1994

Magnetic resonance spectroscopy applied to clinical oncology.

Magnetic resonance spectroscopy provides a means of non-invasively measuring the behaviour of a range of compounds of biochemical significance. With the development of a range of spatial localization and mapping techniques, the method has a range of promising applications in oncology. 31P and 1H spectroscopy are of value in observing the metabolism of both tumours and normal tissues. 19F spectroscopy has been used to monitor the metabolism of fluorine containing anticancer drugs, and 13C may find application in this field, particularly in pre-clinical studies. In vivo clinical measurements are complemented by pre-clinical studies, high resolution measurements of extracts from tissue samples and also the measurement of biofluids, which can provide additional metabolic and pharmacokinetic information. The application of these techniques to oncology is reviewed, with particular emphasis on their clinical role.

Clinical Trials as Topic↗

PubMed1994

Prenatal and perinatal low level lead exposure alters brainstem auditory evoked responses in infants.

Wave III latency and the III-V interpeak interval of brainstem auditory evoked responses in infants in the first weeks of life decreased and increased, respectively, in association with mid-pregnancy maternal blood lead levels (2.5-35 micrograms/dl) in a group of 30 prospectively followed healthy pregnancies and deliveries. The rapid myelination of brainstem auditory pathways occurring around mid-pregnancy and the lengthening of the III-V interpeak interval with increased mid-pregnancy maternal lead suggest that brain structures involved in spatial localization of sound may be compromised by prenatal lead exposure. The data also indicate that maternal blood lead measurements during pregnancy provide an adequate surrogate index of fetal exposure.

Adult↗

PubMed1993

A neurobiological model of visual attention and invariant pattern recognition based on dynamic routing of information.

We present a biologically plausible model of an attentional mechanism for forming position- and scale-invariant representations of objects in the visual world. The model relies on a set of control neurons to dynamically modify the synaptic strengths of intracortical connections so that information from a windowed region of primary visual cortex (V1) is selectively routed to higher cortical areas. Local spatial relationships (i.e., topography) within the attentional window are preserved as information is routed through the cortex. This enables attended objects to be represented in higher cortical areas within an object-centered reference frame that is position and scale invariant. We hypothesize that the pulvinar may provide the control signals for routing information through the cortex. The dynamics of the control neurons are governed by simple differential equations that could be realized by neurobiologically plausible circuits. In preattentive mode, the control neurons receive their input from a low-level "saliency map" representing potentially interesting regions of a scene. During the pattern recognition phase, control neurons are driven by the interaction between top-down (memory) and bottom-up (retinal input) sources. The model respects key neurophysiological, neuroanatomical, and psychophysical data relating to attention, and it makes a variety of experimentally testable predictions.

Animals↗

PubMed1994

A quantitative measure for short-term cortical plasticity in human vision.

The human visual system is normally very good at determining the relative positions of objects in space, but under certain conditions contextual influences can cause significant errors in this process. We studied spatial localization around an artificial scotoma, a small mask that occludes part of the visual field while a dynamic pattern is shown over a surrounding region, and found that the ability to determine the position of short line segments was strongly biased toward the interior of the scotoma. We attribute this "shift" or misassignment of position to receptive field (RF) expansions within the artificial scotoma as seen in recent physiological studies. Furthermore, our findings show that this shift begins within 1 sec of stimulus presentation, suggesting that RFs are constantly altered by their local context and that these dynamics are a part of normal vision.

Humans↗