Molecular genetics of Usher syndrome -inherited deafness and blindness

Usher syndrome (USH) is an inherited blindness and deafness disorder with variable vestibular dysfunction. The syndrome is divided into three subtypes according to the progression and severity of clinical symptoms. The gene mutated in Usher syndrome type 3 (USH3), clarin 1 (CLRN1), was identified in Finland in 2001 and two mutations were identified in Finnish patients at that time. Prior to this thesis study, the two CLRN1 gene mutations were the only USH mutations identified in Finnish USH patients. To further clarify the Finnish USH mutation spectrum, all nine USH genes were studied. Seven mutations were identified: one was a previously known mutation in CLRN1, four were novel mutations in myosin VIIa (MYO7A) and two were a novel and a previously known mutation in usherin (USH2A). Another aim of this thesis research was to further study the structure and function of the CLRN1 gene, and to clarify the effects of mutations on protein function. The search for new splice variants resulted in the identification of eight novel splice variants in addition to the three splice variants that were already known prior to this study. Studies of the possible promoter regions for these splice variants showed the most active region included the 1000 bases upstream of the translation start site in the first exon of the main three exon splice variant. The 232 aa CLRN1 protein encoded by the main (three-exon) splice variant was transported to the plasma membrane when expressed in cultured cells. Western blot studies suggested that CLRN1 forms dimers and multimers. The CLRN1 mutant proteins studied were retained in the endoplasmic reticulum (ER) and some of the USH3 mutations caused CLRN1 to be unstable. During this study, two novel CLRN1 sequence alterations were identified and their pathogenicity was studied with cell culture protein expression. Previous studies with mice had shown that Clrn1 is expressed in mouse cochlear hair cells and spiral ganglion cells, but the expression profile in mouse retina remained unknown. The Clrn1 knockout mice display cochlear cell disruption/death, but do not have a retinal phenotype. The zebrafish, Danio rerio, clrn1 was found to be expressed in hair cells associated with hearing and balance. Clrn1 expression was also found in the inner nuclear layer (INL), photoreceptor layer and retinal pigment epithelium layer (RPE) of the zebrafish retina. When Clrn1 production was knocked down with injected morpholino oligonucleotides (MO) targeting Clrn1 translation or correct splicing, the zebrafish larvae showed symptoms similar to USH3 patients. These larvae had balance/hearing problems and reduced response to visual stimuli. The knowledge this thesis research has provided about the mutations in USH genes and the Finnish USH mutation spectrum are important in USH patient diagnostics. The extended information about the structure and function of CLRN1 is a step further in exploring USH3 pathogenesis caused by mutated CLRN1 as well as a step in finding a cure for the disease.

Characterization of the TRIM37 gene and mutations underlying mulibrey nanism

Mulibrey nanism is a hereditary developmental disorder, characterized by prenatal onset growth failure without postnatal catch-up growth, distinctive craniofacial features, progressive cardiopathy and failure of sexual maturation. In addition, the patients develop insulin resistance syndrome and type 2 diabetes and they have an increased risk of developing tumors. The TRIM37 gene that underlies mulibrey nanism encodes for a member of the tripartite motif (TRIM) protein family. The physiological function of TRIM37 and the pathogenetic mechanisms leading from TRIM37 dysfunction to the mulibrey nanism phenotype are unknown. However, TRIM37 localizes at least partially to peroxisomes, and possesses ubiquitin E3-ligase activity. Thus, it may mediate ubiquitin dependent protein degradation, suggesting that accumulation of yet unknown substrate proteins may underlie the disease pathogenesis. In this study, the TRIM37 gene was characterized in detail. A transcription initiation window, with several separate transcription start sites, was identified and the putative promoter region immediately upstream from the transcription initiation window was shown to possess basal promoter activity. Further, several alternative splice variants of the gene were identified, including a highly expressed testis specific variant, encoding for an identical protein product with the main transcript. Expression of TRIM37 mRNA was detected in several different tissues, with highest expression seen in testis and in brain, when the expression patterns of the two major transcripts in different human tissues were studied by quantitative real-time PCR. Several mulibrey nanism patients were studied and thirteen novel mutations in TRIM37 were found, including three mutations (p.Gly322Val, p.Cys109Ser, p.Glu271_Ser287), that are likely to express mutant TRIM37 proteins. These mutations were further shown to alter the subcellular localization of the mutant proteins. Most of the mulibrey nanism associated mutations however, lead to premature termination codons and degradation of mRNA. All the TRIM37 mutations identified to date predict loss-of-function alleles, and thus no phenotype-genotype correlation is seen among the patients. In order to understand the pathogenetic mechanisms underlying mulibrey nanism, an animal model for the disorder is needed. For the development of a Trim37 knock-out mouse, the mouse Trim37 gene was characterized. Alternative splice variants, were identified, including a testis specific variant predicting a longer protein product. Further, a strictly tissue and cell-specific pattern of Trim37 expression was observed in developing and adult mouse tissues, when studied by immunohistochemical methods. This distribution of Trim37 expression in mouse tissues is in agreement with the clinical findings in human mulibrey nanism patients. This thesis work gives new tools for the diagnostics of mulibrey nanism as well as for studying the molecular pathogenesis behind this interesting disorder.

Structure and function of GDNF receptor alpha splice variants

The growth factors of the glial cell line-derived neurotrophic factor (GDNF) family consisting of GDNF, neurturin (NRTN), artemin (ARTN) and persephin (PSPN), are involved in the development, differentiation and maintenance of many types of neurons. They also have important functions outside the nervous system in the development of kidney, testis and thyroid gland. Each of these GFLs preferentially binds to one of the glycosylphosphatidylinositol (GPI)-anchored GDNF family receptors α (GFRα). GDNF binds to GFRα1, NRTN to GFRα2, ARTN to GFRα3 and PSPN to GFRα4. The GFLs in the complex with their cognate GFRα receptors all bind to and signal through the receptor tyrosine kinase RET. Alternative splicing of the mouse GFRα4 gene yields three splice isoforms. These had been described as putative GPI-anchored, transmembrane and soluble forms. My goal was to characterise the function of the different forms of mouse GFRα4. I firstly found that the putative GPI-anchored GFRα4 (GFRα4-GPI) is glycosylated, membrane-bound, GPI-anchored and interacts with PSPN and RET. We also showed that mouse GFRα4-GPI mediates PSPN-induced phosphorylation of RET, promotes PSPN-dependent neuronal differentiation of the rat pheochromocytoma cell line PC6-3 and PSPN-dependent survival of cerebellar granule neurons (CGN). However, although this receptor can mediate PSPN-signalling and activate RET, GFRα4-GPI does not recruit RET into lipid rafts. The recruitment of RET into lipid rafts has previously been thought to be a crucial event for GDNF- and GFL-mediated signalling via RET. I secondly demonstrated that the putative transmembrane GFRα4 (GFRα4-TM) is indeed a real transmembrane GFRα4 protein. Although it has a weak binding capacity for PSPN, it can not mediate PSPN-dependent phosphorylation of RET, neuronal differentiation or survival. These data show that GFRα4-TM is inactive as a receptor for PSPN. Surprisingly, GFRα4-TM can negatively regulate PSPN-mediated signalling via GFRα4-GPI. GFRα4-TM interacts with GFRα4-GPI and blocks PSPN-induced phosphorylation of RET, neuronal differentiation as well as survival. Taken together, our data show that GFRα4-TM may act as a dominant negative inhibitor of PSPN-mediated signaling. The most exciting part of my work was the finding that the putative soluble GFRα4 (GFRα4-sol) can form homodimers and function as an agonist of the RET receptor. In the absence of PSPN, GFRα4-sol can promote the phosphorylation of RET, trigger the activation of the PI-3K/AKT pathway, induce neuronal differentiation and support the survival of CGN. Our findings are in line with a recent publication showing the GFRα4-sol might contribute to the inherited cancer syndrome multiple endocrine neoplasia type 2. Our data provide an explanation to how GFRα4-sol may cause or modify the disease. Mammalian GFRα4 receptors all lack the first Cys-rich domain which is present in other GFRα receptors. In the final part of my work I have studied the function of this particular domain. I created a truncated GFRα1 construct lacking the first Cys-rich domain. Using binding assays in both cellular and cell-free systems, phosphorylation assays with RET, as well as neurite outgrowth assays, we found that the first Cys-rich domain contributes to an optimal function of GFRα1, by stabilizing the interaction between GDNF and GFRα1.

Untersuchungen zur Fachsprache der Ökologie und des Umweltschutzes im Deutschen und Finnischen : Bezeichnungsvarianten unter einem geschichtlichen, lexikographischen, morphologischen und linguistisch-pragmatischen Aspekt

The work integrates research in the language and terminology of various fields with lexicography, etymology, semantics, word formation, and pragmatics. Additionally, examination of German and Finnish provides the work with perspective of contrastive linguistics and the translation of texts in specialized fields. The work is an attempt to chart the language, vocabulary, different textual types, and essential communication-connected features of this special field. The study is primary concerned with internal communication within the field of ecology, but it also provides a comparison of the public discussion of environmental issues in Germany and Finland. The work attempts to use textual signs to provide a picture of the literary communication used on the different vertical levels in the central text types within the field. The dictionaries in the fields of environmental issues and ecology for the individual text types are examined primarily from the perspective of their quantity and diversity. One central point of the work is to clarify and collect all of the dictionaries in the field that have been compiled thus far in which German and/or Finnish ware included. Ecology and environmental protection are closely linked not only to each other but also to many other scientific fields. Consequently, the language of the environmental field has acquired an abundance of influences and vocabulary from the language of the special fields close to it as well as from that of politics and various areas of public administration. The work also demonstrates how the popularization of environmental terminology often leads to semantic distortion. Traditionally, scientific texts have used the smallest number of expressions, the purpose of which is to appeal to or influence the behavior of the text recipient. Particularly in Germany, those who support or oppose measures to protect the environment have long been making concerted efforts to represent their own views in the language that they use. When discussing controversial issues competing designations for the same referent or concept are used in accordance with the interest group to which the speaker belongs. One of the objectives of the study is to sensitize recipients of texts to notice the euphemistic expressions that occur in German and Finnish texts dealing with issues that are sensitive from the standpoint of environmental policy. One particular feature of the field is the wealth and large number of variants designating the same entry or concept. The terminological doublets formed by words of foreign origin and their German or Finnish language equivalents are quite typical of the field. Methods of corpus linguistics are used to determine the reasons for the large number of variant designations as well as their functionality.

Agreement Patterns in English : Diachronic Corpus Studies on Common-Number Pronouns

This study reports a diachronic corpus investigation of common-number pronouns used to convey unknown or otherwise unspecified reference. The study charts agreement patterns in these pronouns in various diachronic and synchronic corpora. The objective is to provide base-line data on variant frequencies and distributions in the history of English, as there are no previous systematic corpus-based observations on this topic. This study seeks to answer the questions of how pronoun use is linked with the overall typological development in English and how their diachronic evolution is embedded in the linguistic and social structures in which they are used. The theoretical framework draws on corpus linguistics and historical sociolinguistics, grammaticalisation, diachronic typology, and multivariate analysis of modelling sociolinguistic variation. The method employs quantitative corpus analyses from two main electronic corpora, one from Modern English and the other from Present-day English. The Modern English material is the Corpus of Early English Correspondence, and the time frame covered is 1500-1800. The written component of the British National Corpus is used in the Present-day English investigations. In addition, the study draws supplementary data from other electronic corpora. The material is used to compare the frequencies and distributions of common-number pronouns between these two time periods. The study limits the common-number uses to two subsystems, one anaphoric to grammatically singular antecedents and one cataphoric, in which the pronoun is followed by a relative clause. Various statistical tools are used to process the data, ranging from cross-tabulations to multivariate VARBRUL analyses in which the effects of sociolinguistic and systemic parameters are assessed to model their impact on the dependent variable. This study shows how one pronoun type has extended its uses in both subsystems, an increase linked with grammaticalisation and the changes in other pronouns in English through the centuries. The variationist sociolinguistic analysis charts how grammaticalisation in the subsystems is embedded in the linguistic and social structures in which the pronouns are used. The study suggests a scale of two statistical generalisations of various sociolinguistic factors which contribute to grammaticalisation and its embedding at various stages of the process.

Intermediate Past BE : A Paradigm Reshaped With Data Drawn From HARES

In this paper, I look into a grammatical phenomenon found among speakers of the Cambridgeshire dialect of English. According to my hypothesis, the phenomenon is a new entry into the past BE verb paradigm in the English language. In my paper, I claim that the structure I have found complements the existing two verb forms, was and were, with a third verb form that I have labelled ‘intermediate past BE’. The paper is divided into two parts. In the first section, I introduce the theoretical ground for the study of variation, which is founded on empiricist principles. In variationist linguistics, the main claim is that heterogeneous language use is structured and ordered. In the last 50 years of history in modern linguistics, this claim is controversial. In the 1960s, the generativist movement spearheaded by Noam Chomsky diverted attention away from grammatical theories that are based on empirical observations. The generativists steered away from language diversity, variation and change in favour of generalisations, abstractions and universalist claims. The theoretical part of my paper goes through the main points of the variationist agenda and concludes that abandoning the concept of language variation in linguistics is harmful for both theory and methodology. In the method part of the paper, I present the Helsinki Archive of Regional English Speech (HARES) corpus. It is an audio archive that contains interviews conducted in England in the 1970s and 1980s. The interviews were done in accordance to methods used generally in traditional dialectology. The informants are mostly elderly male people who have lived in the same region throughout their lives and who have left school at an early age. The interviews are actually conversations: the interviewer allowed the informant to pick the topic of conversation to induce a maximally relaxed and comfortable atmosphere and thus allow the most natural dialect variant to emerge in the informant’s speech. In the paper, the corpus chapter introduces some of the transcription and annotation problems associated with spoken language corpora (especially those containing dialectal speech). Questions surrounding the concept of variation are present in this part of the paper too, as especially transcription work is troubled by the fundamental problem of having to describe the fluctuations of everyday speech in text. In the empirical section of the paper, I use HARES to analyse the speech of four informants, with special focus on the emergence of the intermediate past BE variant. My observations and the subsequent analysis permit me to claim that my hypothesis seems to hold. The intermediate variant occupies almost all contexts where one would expect was or were in the informants’ speech. This means that the new variant is integrated into the speakers’ grammars and exemplifies the kind of variation that is at the heart of this paper.

Arkeen pudonnut sibylla : Modernin naisen identiteetin rakentuminen Marja-Liisa Vartion romaanissa Kaikki naiset näkevät unia

A Sibyl fallen into everyday life. The enfolding of the identity of modern woman in Marja- Liisa Vartio s novel Kaikki naiset näkevät unia ( All Women Have Dreams ). --- Marja-Liisa Vartio played a remarkable part in renewing Finnish literature. My thesis examines her novel Kaikki naiset näkevät unia (1960), which describes the life of a middle-aged housewife, Mrs. Pyy ( Mrs. Hazel Hen ). She has moved from country to city and lives now in a suburb, in the Helsinki of the 1950 s. In Finnish literature, the novel is the first significant description of a modern city woman accomplished by modernistic means. My research examines the identity of a woman in the Finland of the 50 s, an epoch marked by the inevitable transition into modernity. My aim is to look into the ways in which the female identity enfolds in Kaikki naiset näkevät unia, how it takes its form, how it is described and commented. The primary method is contextual close reading; the novel is seen in the social, cultural and historical context of the time it was published. Essential elements in this study are literary motifs and images in the novel, and particularly transtextual relations as defined by Gérald Genette. The focus is on hypertextuality, intertextuality and paratextuality. Kaikki naiset näkevät unia emerges as a modern version of Madame Bovary by Gustave Flaubert. A woman s life spent in illusive dreaming is transferred from a 1900th century bourgeois town in France to a middle class Finnish suburb in the 1950 s. Vartio s novel is a variant of an ancient Finnish ballad I, a bird without a nest , making it into a modern narration of transition. The inner, mental journey from country to city is of great length, and the liminal life in a suburb does not make the passage any easier. Like the lyrical voices in the poetry of Edith Södergran, also Mrs. Pyy finds it hard to discover any values of sisterhood or those of ideal femininity in modern times. In earlier studies of Marja-Liisa Vartio s prose, stress has been laid on the discourse of her narrators and characters, as well as on its modern literary form. In this research, however, urgent allusions to paintings, old and new, are taken into account, since Mrs. Pyy mirrors herself against art, both classical and modern. Principal images in this context are Michelangelo s Sibyls in the ceiling of the Sistine Chapel, and a modern painting, which remains unidentified. Mrs. Pyy turns out to be a tragicomic character, who has magnanimous illusions about herself, but is compelled to accept the fact the she is only a mediocre person. She is nothing more than a first generation city dweller; she is not a modern, aloof outsider but a mere dilettante, who desperately tries to live out modern city life. Kaikki naiset näkevät unia is a striking picture of the 1950 s, a picture that is construed in the consciousness of Mrs. Pyy. We are shown everyday life growing more and more modern after the war and woman s role growing more and more subject to increasing pressure for change.

The Influence of Constantinople on Middle Byzantine Architecture (843-1204) : A typological and morphological approach at the provincial level.

The influence of the architecture of the Byzantine capital spread to the Mediterranean provinces with travelling masters and architects. In this study the architecture of the Constantinopolitan School has been detected on the basis of the typology of churches, completed by certain morphological aspects when necessary. The impact of the Constantinopolitan workshops appears to have been more important than previously realized. This research revealed that the Constantinopolitan composite domed inscribed-cross type or cross-in-square spread everywhere to the Balkans and it was assumed soon by the local schools of architecture. In addition, two novel variants were invented on the basis of this model: the semi-composite type and the so-called Athonite type. In the latter variant lateral conches, choroi, were added for liturgical reasons. Instead, the origin of the domed ambulatory church was partly provincial. One result of this study is that the origin of the Middle Byzantine domed octagonal types was traced to Constantinople. This is attested on the basis of the archaeological evidence. Also some other architectural elements that have not been preserved in the destroyed capital have survived at the provincial level: the domed hexagonal type, the multi-domed superstructure, the pseudo-octagon and the narthex known as the lite. The Constantinopolitan architecture during the period in question was based on the Early Christian and Late Antique forms, practices and innovations and this also emerges at the provincial level.

Meän tapa puhua : Tornionlaakso pellolaisnuorten subjektiivisena paikkana ja murrealueena

This folk linguistic and human geographic study deals with dialect awareness, dialect use and place attachment. The study discusses theoretical and methodological issues current in sociolinguistics suggesting that the study of attitudes should be regarded as a core area in the study of variation and change. Furthermore, it is suggested that instead of putting effort into improving mental mapping methodology (adopted into folk linguistics from behavioural geography of the 1960 s), the more up-to-date thinking of space in geography should be adopted. The region and the dialect are treated as perceptual constructs in the study. The dialect perceptions of high school seniors in the Finnish Tornio Valley are examined trough a triangulation method involving a questionnaire, interviews and dialect recognition test as the research methods. The h in non-initial syllables (e.g. lähethä(ä)n, saunhaan ~ sauhnaan let s go into sauna ) turns out, expectedly, as the most salient feature in the dialect awareness of the locals and in terms of local identity construction. This feature is no longer heard in most of the present dialects of Finnish but is still thriving in the Tornio Valley in the cross-border dialect area. The metathetic variant (saunhaan > sauhnaan into sauna , käymhään > käyhmään to go ) is a characteristic feature of the Tornio Valley dialect. However, individual differences have long been found in the use of the h. This study challenges the essentialist variationist view of social categories (gender) by analysing variation from a quantitative but emic and human geographic point of view. The study shows that the variation of the h is statistically significantly patterned in terms of the degree of feeling of insideness vs. outsideness. New light is shed on the gender differences found in earlier sociolinguistic studies: differences in dialect use between and inside gender groups are illuminated by the fact that, in this case, it is young women who are generally less attached to the local community than young men, but this does not hold for all the individuals. The ideological motivation for preservation of the h seems to be based on the imagined community of Tornio Valley covering both the Swedish and the Finnish valley area. The general image of the dialect area and it s speakers, the shared cognitive dialect boundaries of the locals and the particularly deep level of awaress of the linguistic variation of the h are notable resources of the Tornio valley identity. Hyperdialectic forms analogical to the most frequently attested metathetic forms are found in the interview data, predicting that in this dialect the h will be maintained also in the future.

Kaveriporukasta liiketoiminnaksi : Tuotannon häiriöt ja organisaation oppiminen nopeasti muuttuvassa yrityksessä

In the 1990 s the companies utilizing and producing new information technology, especially so-called new media, were also expected to be forerunners in new forms of work and organization. Researchers anticipated that new, more creative forms of work and the changing content of working life were about to replace old industrial and standardized ways of working. However, research on actual companies in the IT sector revealed a situation where only minor changes to existing organizational forms were seen .Many of the independent companies faced great difficulties trying to survive the rapid changes in the products and production forms in the emerging field. Most of the research on the new media field has been conducted as surveys, and an understanding of the actual everyday work process has remained thin. My research is a longitudinal study of the early phases of one new media company in Finland. The study is an analysis of the challenges the company faced in a rapidly changing business field and the attempts to overcome these challenges. The two main analyses in the study focus on the developmental phases of the company and the disturbances in the production process. Based on these analyses, I study changes and learning at work using the methodological framework of developmental work research. Developmental work research is a Finnish variant of the cultural-historical activity theory applied to the study of learning and transformations at work. The data was gathered over a three-year period of ethnographic fieldwork. I documented the production processes and everyday life in the company as a participant observer. I interviewed key persons, video and audio-taped meetings, followed e-mail correspondence and collected various documents, such as agreements and memos. I developed a systematic method for analyzing the disturbances in the production process by combining the various data sources. The systematic analysis of the disturbances depicted a very complex and only partly managed production process. The production process had a long duration, and no single actor had an understanding of it as a whole. Most of the disturbances had to do with the customer relationships. The nature of the disturbances was latent; they were recognized but not addressed. In the particular production processes that I analyzed, the ending life span of a particular product, a CD-ROM, became obvious. This finding can be interpreted in relation to the developmental phase of the production and the transformation of the field as a whole. Based on the analysis of the developmental phases and the disturbances, I formulate a hypothesis of the contradictions and developmental potentials of the activity studied. The conclusions of the study challenge the existing understanding of how to conceptualize and study organizational learning in production work. Most theories of organizational learning do not address qualitative changes in production nor historical challenges of organizational learning itself. My study opens up a new horizon in understanding organizational learning in a rapidly changing field where a learning culture based on craft or mass production work is insufficient. There is a need for anticipatory and proactive organizational learning. Proactive learning is needed to anticipate the changes in production type, and the life cycles of products.

Feature integration in human vision

The earliest stages of human cortical visual processing can be conceived as extraction of local stimulus features. However, more complex visual functions, such as object recognition, require integration of multiple features. Recently, neural processes underlying feature integration in the visual system have been under intensive study. A specialized mid-level stage preceding the object recognition stage has been proposed to account for the processing of contours, surfaces and shapes as well as configuration. This thesis consists of four experimental, psychophysical studies on human visual feature integration. In two studies, classification image a recently developed psychophysical reverse correlation method was used. In this method visual noise is added to near-threshold stimuli. By investigating the relationship between random features in the noise and observer s perceptual decision in each trial, it is possible to estimate what features of the stimuli are critical for the task. The method allows visualizing the critical features that are used in a psychophysical task directly as a spatial correlation map, yielding an effective "behavioral receptive field". Visual context is known to modulate the perception of stimulus features. Some of these interactions are quite complex, and it is not known whether they reflect early or late stages of perceptual processing. The first study investigated the mechanisms of collinear facilitation, where nearby collinear Gabor flankers increase the detectability of a central Gabor. The behavioral receptive field of the mechanism mediating the detection of the central Gabor stimulus was measured by the classification image method. The results show that collinear flankers increase the extent of the behavioral receptive field for the central Gabor, in the direction of the flankers. The increased sensitivity at the ends of the receptive field suggests a low-level explanation for the facilitation. The second study investigated how visual features are integrated into percepts of surface brightness. A novel variant of the classification image method with brightness matching task was used. Many theories assume that perceived brightness is based on the analysis of luminance border features. Here, for the first time this assumption was directly tested. The classification images show that the perceived brightness of both an illusory Craik-O Brien-Cornsweet stimulus and a real uniform step stimulus depends solely on the border. Moreover, the spatial tuning of the features remains almost constant when the stimulus size is changed, suggesting that brightness perception is based on the output of a single spatial frequency channel. The third and fourth studies investigated global form integration in random-dot Glass patterns. In these patterns, a global form can be immediately perceived, if even a small proportion of random dots are paired to dipoles according to a geometrical rule. In the third study the discrimination of orientation structure in highly coherent concentric and Cartesian (straight) Glass patterns was measured. The results showed that the global form was more efficiently discriminated in concentric patterns. The fourth study investigated how form detectability depends on the global regularity of the Glass pattern. The local structure was either Cartesian or curved. It was shown that randomizing the local orientation deteriorated the performance only with the curved pattern. The results give support for the idea that curved and Cartesian patterns are processed in at least partially separate neural systems.

Expression of cytochrome P450 enzymes and metabolism of timolol in human ocular tissue

Glaucoma is a group of progressive optic neuropathies causing irreversible blindness if not diagnosed and treated in the early state of progression. Disease is often, but not always, associated with increased intraocular pressure (IOP), which is also the most important risk factor for glaucoma. Ophthlamic timolol preparations have been used for decades to lower increased intraocular pressure (IOP). Timolol is locally well tolerated but may cause e.g. cardiovascular and pulmonary adverse effects due to systemic absorption. It has been reported that approximately 80% of a topically administered eye drop is systemically absorbed. However, only limited information is available on timolol metabolism in the liver or especially in the human eye. The aim of this work was to investigate metabolism of timolol in human liver and human ocular tissues. The expression of drug metabolizing cytochrome P450 (CYP) enzymes in the human ciliary epithelial cells was studied. The metabolism of timolol and the interaction potential of timolol with other commercially available medicines were investigated in vitro using different liver preparations. The absorption of timolol to the aqueous humor from two commercially available products: 0.1% eye gel and 0.5% eye drops and the presence of timolol metabolites in the aqueous humor were investigated in a clinical trial. Timolol was confirmed to be metabolized mainly by CYP2D6 as previously suggested. Potent CYP2D6 inhibitors especially fluoxetine, paroxetine and quinidine inhibited the metabolism of timolol. The inhibition may be of clinical significance in patients using ophthalmic timolol products. CYP1A1 and CYP1B1 mRNAs were expressed in the human ciliary epithelial cells. CYP1B1 was also expressed at protein level and the expression was strongly induced by a known potent CYP1B1 inducer 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The CYP1B1 induction is suggested to be mediated by aryl hydrocarbon receptor (AHR). Low levels of CYP2D6 mRNA splice variants were expressed in the human ciliary epithelial cells and very low levels of timolol metabolites were detected in the human aqueous humor. It seems that negligible amount of CYP2D6 protein is expressed in the human ocular tissues. Timolol 0.1% eye gel leads to aqueous humor concentration high enough to achieve therapeutic effect. Inter-individual variation in concentrations is low and intraocular as well as systemic safety can be increased when using this product with lower timolol concentration instead of timolol 0.5% eye drops.