Česnavičienė, Irena

Parazitologijos mokslas Lietuvoje turi ilgą ir reikšmingą istoriją, glaudžiai susijusią su šalies gamtos ypatumais, žemės ūkio tradicijomis ir visuomenės sveikatos poreikiais. Šiandienos pasaulyje, susiduriant su klimato kaita, globalizacija ir naujų infekcinių ligų atsiradimu, parazitologijos reikšmė Lietuvoje dar labiau padidėja. Klimato ir geografinės sąlygos sudaro palankias sąlygas veistis Įvairiems parazitams, plėstis parazitų pernešėjų arealams, o tai kelia naujus iššūkius visuomenės sveikatai ir biologinei Įvairovei. Parazitologijos studijų dalykas mūsų Universitete nuėjo ilgą evoliucijos kelią, keitėsi studijų programos, mokymo priemonės, gilėjo patirtis. Ši patirtis (buvusių ir esamų) Biologinių sistemų ir genetinių tyrimų instituto darbuotojų perduodama Jums, mieli skaitytojai. Mūsų parengta mokomoji knyga skiriama pirmojo kurso studentams, studijuojantiems biomedicinos mokslus - mediciną, odontologiją, burnos higieną, slaugą ir visuomenės sveikatą. Leidinyje pateikiamas parazitologijos kursas, apimantis svarbiausius žmogaus parazitus, jų morfologiją, sukeliamas ligas, diagnostikos principus ir profilaktikos priemones. Šias teorines žinias padės įtvirtinti praktikos darbai. Kiekvieno praktikos darbo pabaigoje pateikiami saviruošos klausimai, skirti suprasti ir Įsiminti praktikos darbų metu analizuojamus parazitus. Tikimės, kad šis leidinys bus naudingas ne tik pratybų metu, bet ir savarankiškai mokantis, ruošiantis atsiskaitymams arba rengiant baigiamuosius darbus.

Tai, kas atrodė neįmanoma prieš trisdešimt metų, tampa realybe. Šios mokomosios knygos autoriai mano, kad tikrai žengiame individualizuotos medicinos link. 1990 metais pradėtas žmogaus genomo sekoskaitos projektas. Nuo 2014 metų atliekama viso genomo sekoskaita atskiriems pacientams. Klinikine rutina tampa viso egzomo ar net genomo tyrimai. CRISPR/Cas9 genų redagavimas leidžia plačiau taikyti genų terapiją, o Lietuvoje genų terapija pradedami gydyti pirmieji pacientai. Nepaisant įspūdingų galimybių, norėtųsi, kad nepamirštume istorijos, todėl įžangą tęsiame tais pačiais žodžiais, kuriais prasidėjo 2006, 2009, 2013 ir 2021 metais parašytų „Genetikos pratybų“ pratarmės: „Genetikos dėstymo pradžia ne tik Lietuvos sveikatos mokslų universitete, bet ir Lietuvoje sietina su prof. Tado Ivanausko (1882-1970) vardu. Profesorius T. Ivanauskas į paskutinę semestro paskaitą atsinešdavo plakatus su „Mendelio žirneliais“ ir paaškindavo studentams „uždraustuosius paveldimumo dėsnius.“ Genetikos studijų dalykas mūsų Universitete nuėjo ilgą evoliucijos kelią. Vadovaujant buvusiems KMI (vėliau KMA ir KMU) Biologijos katedros vadovams doc. J. Lapinskaitei ir prof. A. Bertuliui, citogenetikos mokslo pradininkams Lietuvoje prof. A. Sinkui ir doc. L Andriuškevičiūtei, keitėsi studijų programos, mokymo priemonės, gilėjo patirtis. Ši patirtis (buvusių ir esamų) instituto darbuotojų ir yra perduodama Jums, mieli skaitytojai. Ši mokomoji knyga skiriama visiems, studijuojantiems mediciną. Bet pravers ir Slaugos, Odontologijos, Visuomenės sveikatos fakultetų studentams. Visi praktikos darbai peržiūrėti ir pataisyti pagal naują Medicinos fakulteto studentams patvirtintą programą. Kiekvieno praktikos darbo pabaigoje nurodyta pagrindinė ir papildoma literatūra, interneto tinklalapiai, užduotys, skirtos studentų praktikos darbams.

The aim of the study was the illusion of the stimulus size depending on the configuration of the stimulus contour. Incomplete contour stimuli were obtained by removing from the pentagon: either a horizontal, vertical, or diagonal contour line, or a combination of lines forming the angle or rectangle. The expansion effect was always present without any exceptions, as in psychophysical experiments with stimuli of full contours. If the lower horizontal line was not present in the contour of the pentagon, the illusion did not change much, 8 to 9 arc min. When two lower lines, horizontal and diagonal were absent, there was an increase in strength of the illusion from 8 to 13 arc min. Apparently, this happened because the angular component was destroyed and the effect of the Müller-Lyer inner wings, causing a reduction in distance, weakened. If only the angular component, a pair of wings, was exposed, the strength of the illusion did not decrease, although the stimulus became shorter than the entire figure. On the contrary, there was an increase of the illusion from 8 to 13 arc min. Thus, the ratio of the effects of expansion and reduction changed. The expansion was on the decline, and the reduction was also declining, but to a higher degree. If the angular component was absent, and the contour of the open rectangle remained, the stimulus became shorter again. But the illusion significantly increased (8 to 17 arc min) referring to the strengthening of the expansion effect and weakening of reduction. For two horizontal lines, the result slightly increased. For the full rectangle, the illusion has also increased. In general, the ratio of expansion and reduction processes varied greatly in the responses to the stimuli during the length matching procedure. The local components of the stimuli were clearly affected by the configurations to which they belonged. The visual perception of the form cannot be divided into the perception of components and folded back like geometric drawings. When separated, any single segment, such as a line, angle, and the rest of the figure, become new visual wholes, regardless of the fact that the mosaic of excitations caused by them in the retina remains almost unchanged. The main factor of perceived distortions in the size of visual stimuli should be considered the functional relationships of the contour segments forming the shape, and not the integration of neural reactions for each segment.

In psychophysical experiments with illusory Kanizsa-type rectangles, observers perceived the distance between non-existent boundaries as longer than determined by the stimulus drawings. The elongation value gradually grew when the length of rectangles increased similar to experiments with real contoured and filled rectangles. In experiments with the Oppel-Kundt stimulus, according to the classics, the perceived length of the filled interval first increased from zero to maximum and then slightly decreased with the number of stripes (0–30). If the filling stripes were removed from the stimulus, but their endpoints remained, the perceptual errors did not disappear, only the experimental curve decreased somewhat, and the maximum smoothed. If two horizontal lines were added to the filled Oppel-Kundt stimulus interval, forming a contour rectangle, the perceptual errors were also pre-sent but remained approximately stable with various numbers of the filling stripes, and the curve approached the horizontal line. The data obtained showed that illusory contours could be as effective as real edges in the genesis of size expansion. The sense of illusory outline arose and intensified with increasing number of points in the line. The results confirmed the assumption that the Oppel-Kundt effect is an individual case of a general sensory phenomenon: the illusion of the size of visual objects. The decisive feature of the Oppel-Kundt object is horizontal illusory contours. The filling stripes themselves area uxiliary functional factors that, indicating the properties of the stimulus surface, emphasize its edges.

We studied the manifestation of the size illusion for four filled geometric shapes: squares, circles, rhombuses and equilateral triangles. In psychophysical experiments, the subjects adjusted the empty interval of the two-part stimulus so that it was equal to the width of the figures the area of which varied within the 0.08 – 10.24 deg2 interval. According to the averaged data for four subjects, the strength of the illusion gradually increased with an increase in the area of squares and triangles, but decreased with an increase in the area of circles and rhombuses. The data obtained can be explained by an interaction of two opposite physiological processes: i/ an increase in the size of an object and ii/ a reduction in distance between two terminal points. Presumably, the expansion of the perceived width occurred for all four figures due to positional shifts in the profiles of the neural excitations caused by the boundaries of the objects. The larger the object was, the greater the positions shifted. But the expansion effect was only apparent for the squares and triangles. In the rhombuses and circles, the lateral segments of the contours played the role of two pairs of inner Müller-Lyer wings, due to which the distance between the endpoints was reduced, therefore, the expansion effect was greatly decreased. The resulting misperception weakened or even became negative when the area of the rhombuses and circles increased. The reduction in distance was greater for rhombuses than for circles, assumingly due to the straight lines of the wings. There was only one pair of wings in the triangles, so the effect of shortening the distance was present but weaker than the effect of expansion. Conclusions: A. The shape of the contour of an object is the main factor determining the strength and sign of the distortions of the perceived size of visual objects. B. The effect of distance reduction may prevail the phenomenon of the size expansion in strength.

A range of computer programing packages for psychophysical methods including open source are available at present. But there are not many convenient and enough flexible experiment control tools that incorporates these methods. The current MATLAB and GNU Octave environment-based project PsyExTool is aimed to create a tool that enables to couple the methods with visual or audio stimulus presentation modules. At present the program allows to use adjustment, constant stimulus and adaptive PSI psychophysical methods. The parameters of the stimulus and psychophysical method is adjusted in a single graphical user interface. The responses are collected using keyboard or mouse. The process of experiment is displayed graphically. At the end of the session, the data can be stored or exported for further analysis. The structure of the program may incorporate and combine additional methods for data collection and stimuli presentation in various sensory modalities. The open-source status of the code should ensure availability and flexibility of the tool.

The aim of the study was the influence of the configuration of the stimulus contour on the illusion of the stimulus size. Horizontally oriented isosceles triangles, rectangles and hybrid stimuli (irregular pentagons) were presented on the monitor screen as empty contour shapes. All stimuli were equal in length and height (180×72 arc min). The triangle apex angle was 23o. The angle of the peak apexes of the hybrid stimuli was changing by steps in the 23o–180o range. As the angles increased in presentations, the diagonal edges of the irregular pentagons became shorter and the horizontal segments grew longer. The subjects adjusted the empty interval of the bipartite stimulus so that it was perceptually equal to the length of the figures, and the mistakes made were considered the values of the illusion of the size of the object. The data obtained showed: i/ the rectangles caused the strongest illusion (9.3%); ii/ the illusion for the triangles was less strong: those the vertices of which were situated at the center of the stimulus caused the 8.5% distortions and the others with vertices at the outer end of the stimulus provided the 3.2% illusion strength; iii/ the illusion of the hybrid stimuli was the weakest (0.7 – 6.3 %). We assume that the global shape, the spatial combination of line segments forming angles and, finally, a closed contour was the main factor of the perceived distortions of the size of the visual stimuli. The positional shifts in the pattern of excitation of an integral contour determined the resulting percept of an object size rather than the sum of shifts in excitations of the separate contour components. The displacements in the excitation pattern might occurred at the level of the grouped associative fields forming the intermediate-level mechanisms of integration of excitations of closed contours. It is well known that the intermediate mechanisms show strong attentional modulation. Att[...].

The purpose of the study was to evaluate the influence of the stimulus shape on the object-size illusion. Rhombuses, rectangles, and hybrid stimuli (elongated hexagons) were presented on the monitor screen as the shapes of blank contours or filled blocks. All stimuli were equal in length and height (180×72 arc min). The rhombus apex angle was 44 deg. The angle of the peak apexes of the hybrid stimuli was changing by steps in the 49-148 deg. range.As the angles were increasing in presentations, the diagonal edges, consequently, were shortening and the horizontal one’s lengthening. In all subjects’ data, the illusion of rhombuses was weaker (2-10%) than that of rectangles (5 to 30%). For some individuals, the rhombuses caused a negative illusion value. The hybrid stimuli produced medium-sized errors that can be arranged in an ascending order according to the apex angle growth: as the shape of the stimulus approached the rectangle, the illusion was increasing, and as it approached the diamond, the illusion strength was decreasing. For the blank and filled stimuli, the illusion magnitude orders were similar to each other, and the curves practically overlapped. To conclude, the angle component in the stimulus contour suppressed the stimulus-size-expansion effect.

This laboratory activity book was designed at the Biology Systems and Genetic Research Institute of the Lithuanian University of Health Sciences for the first year biomedical science students of the Faculties of Medicine and Odontology. Together with the step-by-step guide for the parasitology labs, the workbook provides some theoretical background, which can also be used for individual studies, practical training, studying of other disciplines such as Pharmacy, Oral Hygiene, Occupational Therapy, Public Health, Nursing and Infectious Diseases and for the preparation of Bachelor's and Master's theses. We would like to thank Prof. Dalia Pangonytė and Dr. Milda Kuprytė (Clinic of Pathological Anatomy), Prof. Algimantas Kriščiukaitis and Dr. Robertas Petrolis (Department of Physics, Mathematics and Biophysics) and everyone who contributed to this publication with their insights, suggestions and technical support. Also we thank Rūta Slavinskienė for the translation of this whole book from Lithuanian into English language, and Mindaugas Mickis for the translation of one capter. The authors thank the students, teachers, and colleagues who helped to improve this workbook. We believe it would largely contribute to the development of other educational materials in the future.

Background and aim: Perception of spatial dimensions of visual objects depends on their shape and surface properties1. Rectangular objects, or simply a contour, appear longer than an empty space of the same length that was simultaneously shown next to the stimulus. According to our latest psychophysical data, other geometric shapes (triangles, ovals, or rhombuses) also cause misperceptions of size, but obviously of different strengths and even signs2. Materials and methods: In the present experiments with the length adjustment procedures, subjects adjusted the empty space of the stimulus to equal the length of the test object. The judgment errors indicated the strength and sign of the object size illusion. Six geometric shapes were tested: a simple line, rhombus, oval, rectangle, and two equilateral triangles with the vertex of one directing toward the stimulus center and with that of the other pointing toward the one of the stimulus ends. Filled and empty stimuli were used. Results: The strength of the illusion and the order of the strengths were different among observers. However, some general regularities have been determined. The vertex of both the empty and filled triangle pointing toward the stimulus center was the most powerful shape to induce the illusion of extent. The triangles of the lateral orientation were twothree times less effective than those directed to the center. The rhombus shape was the weakest stimulus type. The rectangles and ovals were about of the middle strength. The lateral orientation triangles and rhombuses might produce the illusion of the negative sign. The filled shapes provided a somewhat stronger illusion than the empty contours. Conclusions: The data obtained support the assumption that the contours of the visual objects are the main primary determinant of the illusion of the object size.