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Biomedical subjects

A Thiele

Publications and source records attributed to A Thiele.

At least 19 recordsLinked to original sources
PubMed1998

[Retroperitoneal fibrosis and arthritis--a manifestation of the same illness].

Retroperitoneal fibrosis is a disorder in which the retroperitoneal fat is the site of a subacute and chronic inflammatory reaction and is subsequently replaced by dense fibrotic tissue. Rheumatoid nodules are chronic granulomata occurring at sites of pressure and movement, both near the body surface and internally. A 55-year-old sales-manager was admitted to radiation synovectomy after a 5 year history of excessive right and left knee effusions. There were no other clinical or laboratory abnormalities. The patient did not respond to either radioisotope synoviorthesis using radioactive Yttrium (90 Y), or to open synovectomy and prostetic surgery of the right knee. One year later, surgery of left ureter was necessary. Histological findings revealed the diagnosis of Ormond's disease. Comparative histological studies of synovial membrane of knee and retroperitoneal tissues showed local necrosis, fibrin deposition, lining cell proliferation, and infiltration by lymphocytes. Diagnosis of arthritis complicated by retroperitoneal rheumatoid nodules and retroperitoneal fibrosis was made. Serum rheumatoid factor has been negative. For the last 3 years, the patient has been on successful therapy with azathioprine. Rheumatoid nodules of the retroperitoneum have vanished completely and frequency of knee effusions decreased.

Arthritis, Rheumatoid↗
PubMed1997

Synchronization of neuronal activity during stimulus expectation in a direction discrimination task.

The dorsal pathway of the primate brain, especially the middle temporal area (MT or V5) and the superior middle temporal area (MST or V5a), is strongly involved in motion detection. The relation between neural firing rates and psychophysical performance has led to the assumption that the neural code used by these areas consists of the relative discharge rates of neuronal populations. As an additional neural code, temporal correlation of neural activity has been suggested. Our study addresses the involvement of such a code in awake monkeys performing a motion discrimination task. We found significant temporal correlations between simultaneously recorded pairs of units in areas MT and MST and other extrastriate cortical areas. Units recorded from the same electrode were more frequently synchronized than units recorded from different electrodes placed within the same or different cortical areas. Activity synchronization was present in the expectation period before stimulus presentation and could not be induced de novo by the stimulus. Rather, we found a contrast-dependent reduction of correlation strength on stimulus onset. Correlation strength did not vary systematically with stimulus directions. We conclude that under the conditions of this study, temporal decorrelation of MT and MST neurons could be used to detect the stimulus, but synchronization does not convey specific information about its direction of motion and therefore is unlikely to contribute to performance in our direction discrimination task. Activity synchronization in the period before stimulus onset could be related to attentive expectation.

Animals↗
PubMed1997

Visual responses of neurons from areas V1 and MT in a monkey with late onset strabismus: a case study.

One adult monkey (Macaca fascicularis) was investigated psychophysically and electrophysiologically after at least 5 years of late onset esotropic macrostrabismus (squint angle 52 deg). Behavioural tests revealed normal monocular visual and visuomotor functions. No indications of deep amblyopia or oculomotor asymmetry were found. The monkey used the left or right eye alternately at about equal frequencies. Single unit recordings from area VI disclosed a normal ocular dominance distribution. Most VI neurons from both hemispheres received binocular input. Thus, discordant visual information from corresponding retinal locations of the two eyes converged onto the cortical neurons. No evidence for anomalous retinal correspondence was found. Diplopia and confusion must therefore be avoided by suppression of vision through one eye to allow stable, unambiguous perception. Possible suppression was investigated by stimulating a neuron through the same eye when it was actively used for fixation in one set of trials, and when it was not used for fixation in another set of trials. Significant differences in these two stimulus conditions were found in 20/39 neurons from area VI and in 11/34 motion sensitive neurons recorded in the middle superior temporal area (MT). The normalized population activity in VI and MT was higher if cells were stimulated through the fixating eye. The data are discussed with respect to possible suppressive mechanisms helping to prevent double vision in strabismus and in binocular rivalry.

Action Potentials↗
PubMed1997

Eye position effects in monkey cortex. I. Visual and pursuit-related activity in extrastriate areas MT and MST.

We studied the effect of eye position on visual and pursuit-related activity in neurons in the superior temporal sulcus of the macaque monkey. Altogether, 109 neurons from the middle temporal area (area MT) and the medial superior temporal area (area MST) were tested for influence of eye position on their stimulus-driven response in a fixation paradigm. In this paradigm the monitored eye position signal was superimposed onto the stimulus control signal while the monkey fixated at different locations on a screen. This setup guaranteed that an optimized stimulus was moved across the receptive field at the same retinal location for all fixation locations. For 61% of the MT neurons and 82% of the MST neurons the stimulus-induced response was modulated by the position of the eyes in the orbit. Directional selectivity was not influenced by eye position. One hundred sixty-eight neurons exhibited direction-specific responses during smooth tracking eye movements and were tested in a pursuit paradigm. Here the monkey had to track a target that started to move in the preferred direction with constant speed from five different locations on the screen in random order. Pursuit-related activity was modulated by eye position in 78% of the MT neurons as well as in 80% of the MST neurons tested. Neuronal activity varied linearly as a function of both horizontal and vertical eye position for most of the neurons tested in both areas, i.e., two-dimensional regression planes could be approximated to the responses of most of the neurons. The directions of the gradients of these regression planes correlated neither with the preferred stimulus direction tested in the fixation paradigm nor with the preferred tracking direction in the pursuit paradigm. Eighty-six neurons were tested with both the fixation and the pursuit paradigms. The directions of the gradients of the regression planes fit to the responses in both paradigms tended to correlate with each other, i.e., for more than two thirds of the neurons the angular difference between both directions was less than +/-90 degrees. The modulatory effect of the position of the eyes in the orbit proved to balance out at the population level for neurons in areas MT and MST, tested with the fixation as well as the pursuit paradigm. Results are discussed in light of the hypothesis of an ongoing coordinate transformation of the incoming sensory signals into a nonretinocentric representation of the visual field.

Animals↗
PubMed1996

Optic flow processing in monkey STS: a theoretical and experimental approach.

How does the brain process visual information about self-motion? In monkey cortex, the analysis of visual motion is performed by successive areas specialized in different aspects of motion processing. Whereas neurons in the middle temporal (MT) area are direction-selective for local motion, neurons in the medial superior temporal (MST) area respond to motion patterns. A neural network model attempts to link these properties to the psychophysics of human heading detection from optic flow. It proposes that populations of neurons represent specific directions of heading. We quantitatively compared single-unit recordings in area MST with single-neuron simulations in this model. Predictions were derived from simulations and subsequently tested in recorded neurons. Neuronal activities depended on the position of the singular point in the optic flow. Best responses to opposing motions occurred for opposite locations of the singular point in the visual field. Excitation by one type of motion is paired with inhibition by the opposite motion. Activity maxima often occur for peripheral singular points. The averaged recorded shape of the response modulations is sigmoidal, which is in agreement with model predictions. We also tested whether the activity of the neuronal population in MST can represent the directions of heading in our stimuli. A simple least-mean-square minimization could retrieve the direction of heading from the neuronal activities with a precision of 4.3 degrees. Our results show good agreement between the proposed model and the neuronal responses in area MST and further support the hypothesis that area MST is involved in visual navigation.

Animals↗
PubMed1996

Neuronal activity in MST and STPp, but not MT changes systematically with stimulus-independent decisions.

Single units in the middle temporal area (MT), the middle superior temporal area (MST) and the upper part of the superior temporal polysensory area (STPp) of the monkey's brain were recorded during the discrimination of direction of visual motion near contrast threshold. In addition to stimulus-related decisions the monkeys often made stimulus-independent decisions while stimuli were well below detection threshold (contrast < 0.01%), or totally absent. During this condition MT neurones showed no systematic changes in their ongoing activity while in the MST and STPp stimulus-independent decisions in the preferred direction of a given neurone were accompanied by the highest ongoing activity. We take this as evidence for internally generated representations of direction of motion in higher visual areas of the superior temporal sulcus. Neurones involved in the initiation of a decision or action are described for the first time in area STPp.

Animals↗
PubMed1996

Neuronal responses in the motion pathway of the macaque monkey to natural optic flow stimuli.

Neurones in higher visual motion areas in the superior temporal sulcus (STS) of the macaque monkey respond to abstract random dot optic flow stimuli. Higher motion areas may not only represent, but in a next computational stage also analyse the flow field to determine, for instance, the direction of heading for navigation purposes. Real world visual scenes differ in several aspects from these abstract optic flow stimuli. We tested the neuronal response to naturalistic optic flow stimuli which simulated egomotion in different virtual environments and contained different numbers of visual cues. Neuronal activity depended mainly on the position of the focus of expansion rather than on other visual cues. This finding supports the hypothesis that higher motion areas within the STS analyse optic flow in natural scenes and can thus signal the direction of heading.

Animals↗
PubMed1996

Monkey saccadic latency and pursuit velocity show a preference for upward directions of target motion.

Saccadic latency was studied as a function of the direction of sudden target displacements (steps) and of subsequent smooth target motion (ramps) in Macaca fascicularis. The monkey fixated a central spot that suddenly changed its position and then moved constantly at 10 deg s-1, thus eliciting initial saccades and subsequent pursuit eye movements (recorded by a magnetic search-coil technique). Latencies for initial saccades differed markedly in the vertical axis, being shorter in upward than downward directions for both step and ramp components of target motion. Saccadic latency was also related to the mean pursuit velocity, indicating that the oculomotor system accounts for the direction of step and ramp components of target motion in an integrative way.

Animals↗
PubMed1996

Anatomical and physiological investigation of auditory input to the superior colliculus of the echolocating megachiropteran bat Rousettus aegyptiacus.

The objective of this study was to investigate whether a representation of auditory space in the superior colliculus (SC) of the echolocating megachiropteran bat (Rousettus aegyptiacus) exists. Additionally the subcortical auditory connectivity of the SC was investigated. A total of 207 units were recorded in five awake animals while presenting acoustic stimuli (white noise, clicks, and pure tones) at different positions in space. Six units responded to acoustic stimulation. Three of these located within the superficial layers and one located in the intermediate layers were classified as omnidirectional units. Two units were located within the deep layers. One was classified as a hemifield unit, and the other as a frontal unit. All units responded phasically to acoustic stimulation with a latency of 4-150 ms. None of them could be activated by visual stimuli. We further examined the interaction of paired auditory and visual stimulation in 116 visually responsive units. Responses to visual stimulation were markedly altered by acoustic stimulation in 5 units. The influence of the acoustic stimuli was temporally and spatially restricted, and resulted either in a reduction or an elevation of unit responsiveness. Horseradish peroxidase was injected into the SC of eight animals to investigate the auditory subcortical connectivity of the SC. Retrograde labeling in auditory structures was rare compared with labeling found in nonauditory structures (e.g., retina, substantia nigra, parabigeminal nucleus). In auditory structures retrograde labeling was found mainly in the external nucleus of the inferior colliculus and in the nucleus of the brachium of the inferior colliculus. To a lesser extent it was found in the nucleus sagulum and in the area medial to the lemniscal nuclei. In one case the dorsal nucleus of the lateral lemniscus and the anterolateral periolivary nucleus were labeled. Our results reveal only a sparse auditory input into the SC of the flying fox, R. aegyptiacus. On the basis of single-unit recordings, we did not find an elaborate representation of auditory space as it is described for several other species. The existence of auditory and bimodal neurones, in combination with their response properties, nonetheless indicate that there might be a representation of auditory space in the SC of R. aegyptiacus.

Acoustic Stimulation↗
PubMed1994

Association of class II sequences encoding DR1 and DQ5 specificities with hypersensitivity to chironomid allergen Chi t I.

A panel of 188 unrelated Caucasian subjects who were exposed to the larvae of Chironomus thummi (Diptera, nonbiting midges) was HLA-typed by polymerase chain reaction amplification of the second exons of the DRB, DQA1, and DQB1 genes followed by dot-blot hybridization with sequence-specific oligonucleotide probes. Type I sensitization to the allergen Chi t I and a large number of other inhalant allergens was determined by RAST and skin testing. Sixty-one individuals were found to be sensitized to Chi t I, of whom 24 were sensitive to this allergen and to no other allergens tested. Statistical analyses showed that only in the latter group were the HLA-D genes DRB1*0101, DQA1*0101, and DQB1*0501 associated with IgE-responsiveness to Chi t I. These results suggest that HLA associations with responsiveness to certain allergens may be more striking in monosensitized subjects.

Adolescent↗
PubMed1993

Density heterogeneities of hepatitis C virus in human sera due to the binding of beta-lipoproteins and immunoglobulins.

Heterogeneities in the density of hepatitis C virus RNA-carrying material (HCV-RNA-CM) found in human sera (1.03-1.20 g/cm3) are attributed to the binding of low-density lipoproteins and/or of IgG. In some sera HCV-RNA-CM seems to be nearly totally bound to beta-lipoproteins and cannot be precipitated by anti-IgG (gamma); in others more than 95% of HCV-RNA-CM is bound to IgG and cannot be precipitated by anti-beta-lipoprotein. Furthermore, there are sera from which HCV-RNA-CM can be completely be precipitated by either anti-beta-lipoprotein or anti-IgG (gamma), pointing to a binding of the two serum proteins to the same HCV-RNA-CM. There are other sera from which HCV-RNA-CM can be partially precipitated by the one or the other antiserum, leaving behind fractions, which are bound to beta-lipoprotein or to IgG. HCV-RNA-CM cannot be precipitated from some sera either by anti-beta-lipoprotein or by anti-IgG (gamma).

Centrifugation, Density Gradient↗
PubMed1993

DNA typing with digoxigenin-11-dideoxyuridinetriphosphate-labelled oligonucleotide probes enables non-radioactive analysis using a dual detection system: application for screening HLA-DQA1 polymorphisms.

We describe a standardized, highly sensitive, nonradioactive detection procedure for HLA class-II typing of DQA1 alleles and suballeles which has important and cost-effective application in studying HLA disease associations. The procedure involves polymerase chain reaction-based target DNA sequence amplification and dot blotting followed by stringent hybridization with digoxigenin-11-dideoxyuridine triphosphate 3'-end-labelled allele-specific oligonucleotide probes. The dual detection system described here makes this procedure very versatile.

Alleles↗
PubMed1991

Pattern of retinotectal projection in the megachiropteran bat Rousettus aegyptiacus.

The retinotopic organisation of the superior colliculus (SC) in the megachiropteran bat Rousettus aegyptiacus was examined with single and multi-unit recordings and by tracing the retrograde and anterograde transport of horseradish peroxidase (HRP) between the retina and the SC. The pattern of projection of the visual field onto the SC in Rousettus resembles the pattern found in most mammals. The whole of the contralateral visual field is represented and, in addition, a region of the ipsilateral visual field extending 25 degrees beyond the vertical 0 degree meridian. The ipsilateral visual field is represented binocularly in the most anterior 300-500 microns of the rostral pole of the SC. The contralateral visual field up to 25 degrees from the vertical meridian is represented through both eyes for the next 500-800 microns. The peripheral part of the contralateral visual field, 25 degrees-110 degrees from the vertical meridian is seen only by the nasal retina (the monocular crescent) of the contralateral eye and is represented in the caudal part of the SC. Following multiple injections of HRP into one SC, ganglion cells were labeled in both the nasal and temporal hemiretina of the contralateral eye. In the retina ipsilateral to the injection site, labeled cells were restricted to the temporal hemiretina. After injections of HRP into one eye, labeled terminals were found all over the contralateral SC, but in the ipsilateral SC they were restricted to a band that begins 300-500 microns caudal from the rostral pole and extends to the middle of the SC. These results suggest that in Rousettus, unlike the megachiropteran bats described by Pettigrew, Jamieson, Robson, Hall, McAnally, and Cooper (Philosophical Transactions of the Royal Society of London Series B 325:489-559, 1989), the retinotopic organisation of the SC is not primate-like, but follows the general mammalian scheme. As the retinotopic organisation of the SC is not consistent among the megachiropteran bats, the pattern of this projection may not be a useful indicator of their phylogenetic origins.

Animals↗
PubMed1989

Potent leukocidal action of Escherichia coli hemolysin mediated by permeabilization of target cell membranes.

The contribution of Escherichia coli hemolysin (ECH) to bacterial virulence has been considered mainly in context with its hemolytic properties. We here report that this prevalent bacterial cytolysin is the most potent leukocidin known to date. Very low concentrations (approximately 1 ng/ml) of ECH evoke membrane permeability defects in PMN (2-10 x 10(6) cells/ml) leading to an efflux of cellular ATP and influx of propidium iodide. The attacked cells do not appear to repair the membrane lesions. Human serum albumin, high density and low density lipoprotein, and IgG together protect erythrocytes and platelets against attack by even high doses (5-25 micrograms/ml) of ECH. In contrast, PMN are still permeabilized by ECH at low doses (50-250 ng/ml) in the presence of these plasma inactivators. Thus, PMN become preferred targets for attack by ECH in human blood and protein-rich body fluids. Kinetic studies demonstrate that membrane permeabilization is a rapid process, ATP-release commencing within seconds after application of toxin to leukocytes. It is estimated that membrane permeabilization ensues upon binding of approximately 300 molecules ECH/PMN. This process is paralleled by granule exocytosis, and by loss of phagocytic killing capacity of the cells. The recognition that ECH directly counteracts a major immune defence mechanism of the human organism through its attack on granulocytes under physiological conditions sheds new light on its possible role and potential importance as a virulence factor of E. coli.

Adenosine Triphosphate↗
PubMed1985

[Differential analysis of the binding forms of iron in various plant foodstuffs].

In fourteen plant foodstuffs of various composition a differentiation of iron contents according to water soluble, in ethylacetate extractable, in labile contents and iron(II) or Fe(III) species in the water extract are carried out by the spectrophotometric Ferrozine method. High water-soluble labile iron parts and high iron(II) contents were found in fruit, high complexed parts in the water extract and ethylacetate extractable iron contents in protein rich foodstuffs. The iron total contents are situated between 1 and 90 ppm, the water soluble parts amount to 6 up to 60% of the total content according to the foodstuffs.

Acetates↗