Mutations in the KRAS gene in ovarian tumors.

RAS genes are the most frequently mutated oncogenes detected in human cancer. In this study we analyzed the presence of mutations at codon 12 of the KRAS gene in 78 women with ovarian tumor, including 64 invasive ovarian cancers and 14 borderline ovarian tumors, using an RFLP-PCR technique and we evaluated whether such alterations were associated with the selected clinicopathological parameters of the patients. KRAS codon 12 gene mutations were found in 6,2% of ovarian cancer tissue and in 14,3% of the borderline ovarian tumor. KRAS mutations were found with a significantly higher frequency in mucinous and borderline tumors compared to serous tumors (

Prognostic significance of smac/DIABLO in endometrioid endometrial cancer.

Apoptosis may occur via a death receptor-dependent or independent (mitochondrial) pathway. The mitochondrial pathway is regulated by small molecules, such as smac/Diablo, which activates caspase cascades. This study examined smac/DIABLO expression in 76 patients with endometrioid endometrial cancers. Presence of smac/DIABLO was quantified by Western blot analysis using nonfixed fresh frozen tissues. Its appearance was found in 55 (72%) of examined tumors. Smac/DIABLO expression significantly correlated with tumor grade (

Mutations of the KRAS oncogene in endometrial hyperplasia and carcinoma.

The aim of this study was to examine the prevalence and clinicopathological significance of KRAS point mutation in endometrial hyperplasia and carcinoma. We analysed KRAS in 11 cases of complex atypical hyperplasia and in 49 endometrial carcinomas using polymerase chain reaction associated with restriction fragment length polymorphism (PCR-RFPL). Point mutations at codon 12 of KRAS oncogene were identified in 7 of 49 (14,3%) tumor specimens and in 2 of 11 (18,2%) hyperplasias. No correlation was found between KRAS gene mutation and age at onset, histology, grade of differentiation and clinical stage. We conclude that KRAS mutation is a relatively common event in endometrial carcinogenesis, but with no prognostic value

Spalvų suvokimo konstantiškumas: empirinis tyrimas ir matematinis modelis

The method to estimate the color constancy is suggested. The experimental results confirm the hypothesis of color constancy linear model. The linear operator calculated from the chromaticity coordinates of three chips under two different illuminations. The analysis of this linear operator is performed to clear up the physiological mechanism.Straipsnyje pasiūlytas būdas, kaip įvertinti spalvų suvokimo konstantiškumas. Eksperimento rezultatai patvirtino, kad spalvų suvokimo konstantiškumas yra linijinis modelis. Linijinis operatorius buvo apskaičiuotas iš chromatinių koordinačių, gautų iš trijų daviklių dviem apšvietimo sąlygomis. Operatoriaus analizė atlikta, siekiant išaiškinti psichologinį mechanizmą

Spalvų suvokimo konstantiškumo veiksniai: kontrastas ir adaptacija prie fono spalvos

Colour constancy is the ability of the human visual system to comprehend the constant colour of an object with no regard to changes in the illumination spectrum. Each year witnesses the appearance of new scientific works in various countries. The works touch upon different aspects of the phenomenon. Although scientific research has been conducted for many years, there is no recognised theory explaining the mechanisms that are decisive for colour constancy. The aim of the present work was to establish the influence of contrast, adaptation and background structure upon colour constancy.All experiments were performed with the application of asymmetric matching. Five subjects took part in the experiments. Colour constancy was examined by performing experiments in three cycles. The test illuminants were two Planckian illuminants, standard illuminant A (u’= 0.2559, v’ = 0.5243), illuminant S (u’= 0.1744, v’= 0.3923) and illuminants r (u’/v’ = 0.2618/0.4533), g (u’/v’ = 0.1517/0.4667), v (u’/v’ = 0.2116/0.3766), y (u’/v’ = 0.1939/0.5180. The first set of 7/4 (value – 7/, chroma – /4) of 10 Munsell samples served as test stimuli in the experiments of the second cycle. Being 2° in size, they were generated in the centre of the monitor. The samples were surrounded by a neutral background, sized N7 20° (N meaning the colour being neutral, with the value of 7). Around the neutral background, subject of the experiment saw the non-radiating part of the screen, which we called the „black surround“ (Fig. 1). In the second set of the experiment, the subjects observed the stimuli througha cardboard tube (Fig. 2). Neutral N7 Munsell samples and a set of 7/4 (value – 7/, chroma – /4) of 10 Munsell samples served as test stimuli in the experiments of the third cycle.Colour constancy is quantitively evaluated on the basis of the Brunswik Ratio (BR) (Troost and de Weert, 1991). Higher values of BR were associated with longer adaptation periods, but only when a larger background was used (second cycle of experiments (Fig. 7)). Supplementary experiments showed that the changes in colour appearance were related to a slight shift in the perceived colour of the background. The timing of the colour shifts was modelled in terms of cone opponent responses.Our conclusions are:1. When stimuli are exposed for a short period of time (1 s), partial colour constancy takes place. It does not change (or changes insignificantly) when the stimulus is observed for a longer time (5 and 30 s). Such colour constancy is determined by fast processes which confirm the influence of simultaneous contrast on colour constancy.2. When the background is small, the influence of adaptation on colour constancy is little, even it the observation time is long (5 or 30 s).3. When the background fills the entire field of vision, adaptation results in a high colour constancy perception.Straipsnyje keliame hipotezę, kad spalvos suvokimo konstantiškumas, kaip procesas, turi dvi sudedamąsias dalis: lokalų ir globalų procesą. Lokalus procesas – tai skirtumas tarp fono ir spalvoto objekto (mūsų tyrimuose – Manselio pavyzdėlio). Šis procesas nuo adaptacijos nepriklauso ir vyksta tik nedideliame regėjimo lauke. Kitas procesas vyksta bėgant laikui, kai kinta suvokiama spalva. Tai fono spalva. Stebėtojas ją įvertina kaip viso regėjimo lauko spalvinį parametrą, todėl pastarasis procesas – globalus. Spalvų suvokimo konstantiškumo eksperimente abu procesus tyrėme asimetriniu stimulų lyginimo metodu. Bandymams naudojome 7 skirtingus plataus spektro apšvietimo šaltinius. Dviejose skirtingose bandymų serijose testiniai stimulai – Manselio 7/4 pavyzdėliai, buvo generuojami monitoriaus ekrane. Bandymuose dalyvavo penki tiriamieji. Spalvų suvokimo konstantiškumas buvo įvertinamas Brunsviko santykiu (BR). Gauti rezultatai rodo, kad adaptaciniai pokyčiai nevyksta, kai tiriamųjų regos lauke yra „tuščioji aplinka“. Pašalinus „tuščiąją aplinką“, spalvų suvokimo konstantiškumas pagerėja, BR tampa artimas 1. Remdamies bandymų rezultatais galime teigti, kad yra du skirtingi spalvos suvokimo procesai. Vienas yra greitas, beveik šuoliškas, nulemtas kontrasto, o kitas lėtesnis, adaptacinio pobūdžio, aiškiai pastebimas po 30 s. Spalvos pokytis (adaptacija) dar įvertinamas oponentinių signalų atsakų apskaičiavimu

Categorizing facial expressions : a comparison of computational models

The original publication is available at www.springerlink.com Copyright SpringerRecognizing expressions is a key part of human social interaction, and processing of facial expression information is largely automatic for humans, but it is a non-trivial task for a computational system. The purpose of this work is to develop computational models capable of differentiating between a range of human facial expressions. Raw face images are examples of high-dimensional data, so here we use two dimensionality reduction techniques: principal component analysis and curvilinear component analysis. We also preprocess the images with a bank of Gabor filters, so that important features in the face images may be identified. Subsequently, the faces are classified using a support vector machine. We show that it is possible to differentiate faces with a prototypical expression from the neutral expression. Moreover, we can achieve this with data that has been massively reduced in size: in the best case the original images are reduced to just 5 components. We also investigate the effect size on face images, a concept which has not been reported previously on faces. This enables us to identify those areas of the face that are involved in the production of a facial expression.Peer reviewe

Du objektų spalvos suvokimo procesai

Perception of colour depends on the spectral composition of light that reaches retina and depends as well on various mechanisms of visual system that processes information flow. The few important mechanisms can be distinguished in colour perception: colour adaptation, colour constancy and colour contrast. If the visual field has only one coloured object, then colour perception will be determined by spectral composition of the light and colour adaptation. Whereas mechanisms of colour constancy and colour contrast switches on when in the visual field there are at least two colour objects. Von Kries (1905) have attributed colour constancy phenomenon to theory of receptoral adaptation. But this is theory is applicable to local processes happening in relatively small size of visual field. Craven and Foster (1992) shows that receptor excitation ratios remains constant during change of illumination. But again remains unexplained colour change during adaptation. So, the hypothesis is raised that two processes attribute colour perception: local colour contrast calculation and global adaptation to the background. Therefore the experiments have been carried out to establish the colour contrast and background adaptation impact on colour perception.Four subjects with normal colour vision participated in the experiments. 40 Munsell samples (value 7 and chroma 4) illuminated with one reference illuminant (standard C) and 6 test illuminants (standard A, standard S, cardinal red, cardinal green, cardinal yellow and cardinal blue) were simulated on computer monitor. The dark-adapted subjects have been shown colour samples on neutral background illuminated with one of test illuminants. The task was to match the colour stimuli appearance under reference illuminant. The sequential asymmetric matching procedure was carried out. First subject adapts to neutral background under illuminan C then test stimulus and test background appears for limited time followed by readaptation to neutral background. Then subject is asked to adjust the colour mach under illuminant C. Two different experiment paradigms have been used. In the first one the stimulus had 2° on neutral background covering 20° of visual field. In the second paradigm the stimulus size was the same but the background was covering the all visual field. The adaptation and presentation timings were 1, 5, 30 or 60 seconds.Results under the first experiment paradigm show partial colour constancy for all subjects and for all test illuminants under various adaptation times. Despite quite a long adaptation time of 30 seconds subjects was unable to achieve full colour constancy. Colour constancy improves under second experiment paradigm. 60-second adaptation time is enough to achieve full colour constancy. The less adaptation time (1 or 30 second) gives partial colour constancy.The subject sees two colours (stimulus and background) during the experiment. The colour perception of stimulus and background changes during adaptation time. In the first 5 seconds of adaptation 40–60% of full adaptation level is reached (Fairchild and Reniff, 1995; Werner et al., 2000). Wesner and Shevell (1992, 1994) shown that signals from all visual field have influence on colour perception of object. The first part of our experiment shows that neutral background of 20° gives partial adaptation to background colour. Therefore, increase background illumination to full visual field gives full adaptation to background. So, subject perceives different coloured background under various illuminants as the same neutral (grey) background.We can state that two different systems have been distinguished in the process of colour perception. One system evaluates the colour difference between the stimulus and the background. Second system evaluates the colour of the background. Perceived colour difference during adaptation does not change much, but perceived colour of the background changes a lot and drifts towards neutral colour. The hypothesis of two level colour perception is supported by experimental data.  Objektų spalvų suvokimas aiškinamas dviem procesais. Atlikti bandomieji tyrimai, kuriais nustatyta kontrasto ir fono adaptacijos įtaka spalvų suvokimui. Bandyme dalyvavo keturi tiriamieji. Jų spalvinis regėjimas buvo normalus. 40 spalvotų stimulų ir 6 apšvietimai buvo generuojami vaizduoklio ekrane. Tiriamiesiems buvo rodomas spalvotas objektas pilkame fone esant įvairiems apšvietimams. Tiriamasis turėjo nustatyti, kokią objekto spalvą mato esant įvairiems adaptacijos laikams. Paaiškėjo, kad galima išskirti dvi subjektyvaus spalvos įvertinimo sistemas: viena sistema įvertina objekto ir suvokiamo fono spalvų skirtumą, o kita – fono spalvą. Suvokiamas spalvų skirtumas adaptacijos metu keičiasi nedaug, o suvokiama fono spalva artėja prie neutralios. Gauti duomenys pagrindžia dviejų lygmenų spalvų suvokimo hipotezę: sistema, įvertinanti spalvų skirtumus, yra lokali, o sistema, įvertinanti foną, – globali

Fast cyclic stimulus flashing modulates perception of bi-stable figure

Many experiments have demonstrated that the rhythms in the brain influence the initial perceptual information processing. We investigated whether the alternation rate of the perception of a Necker cube depends on the frequency and duration of a flashing Necker cube. We hypothesize that synchronization between the external rhythm of a flashing stimulus and the internal rhythm of neuronal processing should change the alternation rate of a Necker cube. Knowing how a flickering stimulus with a given frequency and duration affects the alternation rate of bistable perception, we could estimate the frequency of the internal neuronal processing. Our results show that the perception time of the dominant stimulus depends on the frequency or duration of the flashing stimuli. The duration of the stimuli, at which the duration of the perceived image was maximal, was repeated periodically at 4 ms intervals. We suppose that such results could be explained by the existence of an internal rhythm of 125 cycles/s for bistable visual perception. We can also suppose that it is not the stimulus duration but the precise timing of the moments of switching on of external stimuli to match the internal stimuli which explains our experimental results. Similarity between the effects of flashing frequency on alternation rate of stimuli perception in present and previously performed experiment on binocular rivalry support the existence of a common mechanism for binocular rivalry and monocular perception of ambiguous figures