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P Moller

Publications and source records attributed to P Moller.

At least 19 recordsLinked to original sources
PubMed1997

Interactions between colour and motion in image segmentation.

BACKGROUND: . An important early stage in visual processing is image segmentation, in which similar regions are grouped together and segregated from dissimilar regions, so that distinct objects ultimately may be located and recognized. In the natural world, objects are simultaneously characterized by colour, motion, texture and other visual attributes. How does the human visual system combine these attributes to segment the image? Although colour and motion information are conveyed by distinct functional streams from retina to visual cortex, there is increasing evidence for early and substantial cross-talk between the streams. Here, we explore psychophysical evidence for interactions between colour and motion in image segmentation. RESULTS: . Observers performed forced-choice segmentation tasks on random-dot stimuli. The dots in the vertical target figure were distinguished from the background dots by a different distribution of speeds or colours. To explore interactions between motion and colour segmentation, we added motion noise to the colour signal (or vice versa) by assigning all dots speeds (or colours) drawn from one of several noise distributions. Motion noise severely affects segmentation by colour. Motion noise defined by a broad distribution of speeds degrades colour segmentation, but a two-speed motion distribution (half moving up, half moving down) facilitates colour segmentation. Control experiments prove that the facilitatory effect is not caused by integrating colour information over different frames, nor can it be explained by probability summation over the two planes of moving dots. Colour noise also affects motion segmentation, but under a more restricted range of conditions, and not in a facilitatory way. CONCLUSIONS: . Colour and motion information interact at early stages during image segmentation, before decisions based on either cue in isolation are made. The robust bipolar effects of motion information on segmentation by colour indicate that the establishment of motion-defined surfaces takes primacy, and that such surfaces constitute important primitives for further processing.

Choice Behavior↗
PubMed1990

The effects of androgens and estrogen on the external morphology and electric organ discharge waveform of Gnathonemus petersii (Mormyridae, Teleostei).

The effects of androgens and estrogen on the external morphology and electric organ discharge (EOD) waveform in Gnathonemus petersii, a weakly discharging electric fish, were investigated. Following preimplant data collection, juvenile and adult fish were gonadectomized and implanted with silastic capsules containing either high or low doses of testosterone (T), dihydrotestosterone (DHT), estradiol-17 beta (E2), or cholesterol. One group of fish was treated with high doses of DHT + E2. Radioimmunoassays revealed that low-dose implants resulted in plasma T levels comparable to and high-dose implants about sixfold greater than those found in adult males imported during breeding season. High-dose E2 implants resulted in higher plasma E2 levels in adults than those in juveniles. At either dose, both androgens induced male-like indentations in the dorsal margin of the anal fin of juveniles and adult females by 4 weeks postimplant. Both low and high doses of T decreased the peak power spectrum frequency (PPSF) of Fourier transformations of EODs and increased the durations of phases 2 and 3 of the EOD in juveniles and adults, but the high doses caused more rapid and profound effects. The two doses of T caused opposite effects on the durations of phases 1 and 4 juveniles. The low dose of T decreased the durations of phases 1 and 4, while the high dose increased them. In adults, the high dose of T increased the duration of phase 1, but had inconsistent effects on the duration of phase 4. Total EOD durations were increased by both doses of T in juveniles, while adults showed inconsistent effects possibly due to individual variability in hormone sensitivity. Compared to T, DHT exerted similar, but less dramatic effects on all measures, but only at high doses. E2 significantly increased adult PPSFs, the first such finding in a mormyrid species. E2 had no effects on juvenile PPSFs, or on adult or juvenile EOD phase durations. The effects of DHT + E2 on PPSF and phases 2 and 3 were similar to those of DHT alone. These findings demonstrate quantifiable steroid-dependent plasticity in the durations of individual phases of EODs in an electric fish and are the first to show that the external morphology in Gnathonemus petersii is androgen-dependent. The results are discussed with regard to methodological considerations and hormone studies involving sex differences in EODs reported for this and other species.

Animals↗
PubMed1990

Production and characterization of monoclonal antibodies to the glycosyl phosphatidylinositol-anchored lymphocyte differentiation antigen ecto-5'-nucleotidase (CD73).

A panel of monoclonal antibodies to the 69 kDa glycosyl phosphatidylinositol anchored lymphocyte differentiation antigen ecto-5'-nucleotidase (ecto-5'-NT, CD73) was produced using highly purified human placental 5'-NT as immunogen. Antibodies 1E9.28.1 and 7G2.2.11 inhibit soluble placental 5'-NT activity and recognize lymphocyte CD73 in indirect immunofluorescence and immunoprecipitation assays. In addition, 1E9.28.1 induces vigorous T cell proliferation in the presence of submitogenic doses of phorbol myristate and F(ab')2 goat anti-mouse Ig. Both antibodies can be used to purify the three major forms of placental 5'-NT by affinity chromatography. By two-color immunofluorescence, CD73 was found to be expressed on 19 +/- 5% of CD3+, 11 +/- 4% of CD4+, 51 +/- 14% of CD8+, 25 +/- 8% of CD28+, 15 +/- 5% of CD29+, 27 +/- 7% of CD45RA+, and 70 +/- 6% of CD19+ lymphocytes. Within T cells, CD73 expression is restricted to the CD28+ subset. Thus, CD73 is found on subsets of both T and B lymphocytes, with the highest expression on B cells and CD8+ T cells. In sections of hyperplastic tonsil, CD73 expression is restricted to the small lymphocytes of the follicular mantle zone, a small subset of extrafollicular lymphocytes situated within the epithelium of the tonsillar crypt, and to follicular dendritic cells within the lower part of the "light-zone." CD73 is also detected on subsets of endothelial cells of capillaries and venules and the basal layer of non-keratinizing squamous epithelium and transitional cell type mucosa of many tissues. Given the tissue distribution of CD73, along with its glycosyl phosphatidylinositol membrane anchoring and the observation that some CD73 antibodies are mitogenic, we propose that this interesting antigen may play a role in cell activation, lymphocyte homing, and/or cell adhesion.

5'-Nucleotidase↗
PubMed1989

Patterns of electric organ discharge activity in the weakly electric fish Brienomyrus niger L. (Mormyridae).

In this study we investigated the electric organ discharge (EOD) activity of the mormyrid fish Brienomyrus niger when they were not affected by conspecific EODs. The fish emitted two types of EOD patterns: phasic and tonic sequences of pulse intervals (SPIs). The phasic SPI occurred in the form of stereotyped, individual-specific bursts in EOD activity which we called scallop. Tonic SPIs varied in mean EOD repetition rate and pulse interval stability, and consisted of either regular activity with mean frequencies exceeding 10 Hz and a coefficient of variation (cv) below 15%, or variable activity with mean rates below 10 Hz and cv's of 15% and above. Individual fish predominantly generated one of the three patterns: "variable", "regular", or "scallop". Most fish emitted "variable" activity, but "regular" activity was typical of females and "scallop" of males. We suggest that these SPIs may facilitate individual recognition. The dynamics of the electromotor command system, as reflected by the fish's EOD activity, is compared with that of the well-studied mammalian inferior olive, and mechanisms for a possible self-regulatory central pattern generator are discussed.

Animals↗
PubMed1988

Testosterone changes the electric organ discharge and external morphology of the mormyrid fish, Gnathonemus petersii (Mormyriformes).

Effects of silastic and pellet methyltestosterone implants on the waveform of the electric organ discharge of the weakly electric African mormyrid, Gnathonemus petersii, were investigated. Within seven days of implantation, the duration of the discharge increased dramatically while the associated peak power frequency of the Fourier spectrum decreased in all treated fish. By day 35, hormone-treated fish exhibited up to five-fold increases in EOD duration, as well as multiple discharges and variations in the shape of the positive phase of the discharge. Testosterone treatment also changed body morphology, making immature and adult female fish resemble adult males.

Animals↗
PubMed1988

Evidence that in vitro adherence of Klebsiella pneumoniae to ciliated hamster tracheal cells is mediated by type 1 fimbriae.

Clinical isolates of fimbriated and nonfimbriated Klebsiella pneumoniae were examined for the ability to adhere to hamster tracheal cells cultured in vitro. Fimbriated-phase K. pneumoniae adhered preferentially to ciliated cells, whereas nonfimbriated-phase organisms were not adherent. The adherence was inhibited by D-mannose but not D-glucose, suggesting that type 1 fimbriae serve as the adhesin in the attachment process.

Animals↗
PubMed1985

Caries prevalence in Icelandic children in 1970 and 1983.

In the autumn of 1983 a clinical survey was carried out on 756 children aged 6-14 yr, residing in three non-fluoridated communities in Iceland. The aim of the survey was to assess what changes, if any, in caries prevalence may have taken place as a result of the provision of free dental restorative services for these children since 1974. The 1983 prevalence data were compared with data obtained from a caries survey conducted in 1970 in the same areas in Iceland. The same examiner performed all examinations in both studies. Although considerable increase was noted in number of filled teeth with a corresponding decrease in carious and missing teeth, a statistically significant change in caries prevalence, (dft, dfs, DMFT, DMFS) did not manifest itself. The dfs and DMFS in 1983 was 8.9 and 9.5, respectively, compared to 8.5 and 10.4 in 1970. Over 90% of the toothpaste used in Iceland during the 1970's contained fluoride. The children in the three study areas had not been provided with any public preventive programs.

Adolescent↗
PubMed1984

Locomotor and electric displays associated with electrolocation during exploratory behavior in mormyrid fish.

In the presence of a novel stimulus such as an aluminum or a plastic rod mormyrid fish (Marcusenius cyprinoides and Gnathonemus petersii) exhibit characteristic motor probing acts (PMAs): 'chin probing', 'radial' and 'lateral va-et-vient', 'lateral probing', 'tangential probing', and 'stationary probing'. During the display of these PMAs the fish maintain characteristic probing distances from the object which were 4.5 cm for the metal and 2.5-3.7 cm for the plastic stimulus. G. petersii with their electric organ rendered inoperative ('silent fish') no longer exhibited 'radial' and 'lateral va-et-vient'. Regardless of the nature of the stimulus the probing distances were shorter in 'silent' fish and ranged from 1.8 to 2.6 cm. During the display of PMAs intact fish changed their variable electric organ discharge rate to a unique and stable, regularized rate, with the interdischarge interval maintained at 28-30 ms. The fish's electric and non-electric (motor) probing behavior in the presence of novel objects (and following their removal during phantom PMAs) is discussed in light of theories on exploratory behavior.

Animals↗
PubMed1980

A renal lesion in ankylosing spondylitis.

2 patients with ankylosing spondylitis (A Sp) were found to have renal lesions similar to those seen in IgA nephropathy. In 1 patient the changes were extremely severe and progressive and in the other they were mild. Vascular changes were also noted in 1 patient. The findings suggest an immune complex mediated glomerulonephritis and support an earlier report that there may be a specific renal lesion in patients with A Sp. The significance of IgA deposition in the mesangium, and of an increase in the serum levels of IgA in some patients with A Sp is unclear.

Adult↗
PubMed1979

Spatial aspects of electrolocation in the mormyrid fish, Gnathonemus petersii.

The range of electrolocation in the weakly electric fish, Gnathonemus petersii, was determined for plastic and aluminium cubes. A characteristic change in the fish's EOD activity, and abrupt change to more uniform EOD intervals (regularization), was used as the criterion for object detection. The average response distances extending laterally from the fish's longitudinal axis were significantly different (p less than 0.05) for the aluminium cube (5.4 cm) and the plastic cube (7.0 cm).

Animals↗
PubMed1976

Electric signals and schooling behavior in a weakly electric fish, Marcusenius cyprinoides L. (Mormyriformes).

Field recordings of electric organ discharges and catches of Marcusenius cyprinoides showed that these electric fish form groups and move about in schools. The role electric organ discharges in group cohesion was investigated by comparing interactions in groups of intact and operated, electrically silent fish. The absence of electric organ dischares reduced locomotor activity and resulted in the disappearance of two behaviors: parallel lineup and single file swimming. Electric signals are considered part of a schooling mechanism that aids the fish in maintaining group cohesion in their turbid enviornment and during migration at night.

Animals↗
PubMed1976

Electric organ discharges of the weakly electric fish Gymnarchus niloticus (Mormyriformes) in its natural habitat.

Electric organ discharges (EODs) of Gymnarchus niloticus in its natural habitat (Chari River, Chad Basin) and accompanying ecological data (pH, conductivity, temperature, turbidity, O2 dissolved) were recorded. The EOD frequencies ranged from 204 to 313 Hz (day) and 196-326 Hz (night). In social swimming the range of interfish EOD frequency differences was from 4 to 82 Hz. The EOD frequency seems to decrease with the age of the fish.

Age Factors↗
PubMed1976

[Dental instrument as foreign body in the air-passage].

A case report on a Kerr-broach aspirated to the left bronchial tree is presented. The broach was removed with difficulties using bronchoscope and forceps. The use of rubber dam is advocated in endodontic therapy. A scheme to handle foreign bodies in the bronchial tree is outlined involving immediate X-ray and removal by an experienced endoscopist.

Bronchi↗